## (C) Copyright 2000 - 2013# Wolfgang Denk, DENX Software Engineering, wd@denx.de.## SPDX-License-Identifier:GPL-2.0+#Summary:========This directory contains the source code for U-Boot, a boot loader forEmbedded boards based on PowerPC, ARM, MIPS and several otherprocessors, which can be installed in a boot ROM and used toinitialize and test the hardware or to download and run applicationcode.The development of U-Boot is closely related to Linux: some parts ofthe source code originate in the Linux source tree, we have someheader files in common, and special provision has been made tosupport booting of Linux images.Some attention has been paid to make this software easilyconfigurable and extendable. For instance, all monitor commands areimplemented with the same call interface, so that it's very easy toadd new commands. Also, instead of permanently adding rarely usedcode (for instance hardware test utilities) to the monitor, you canload and run it dynamically.Status:=======In general, all boards for which a configuration option exists in theMakefile have been tested to some extent and can be considered"working". In fact, many of them are used in production systems.In case of problems see the CHANGELOG and CREDITS files to find outwho contributed the specific port. The boards.cfg file lists boardmaintainers.Note: There is no CHANGELOG file in the actual U-Boot source tree;it can be created dynamically from the Git log using:make CHANGELOGWhere to get help:==================In case you have questions about, problems with or contributions forU-Boot you should send a message to the U-Boot mailing list at<u-boot@lists.denx.de>. There is also an archive of previous trafficon the mailing list - please search the archive before asking FAQ's.Please seehttp://lists.denx.de/pipermail/u-boot andhttp://dir.gmane.org/gmane.comp.boot-loaders.u-bootWhere to get source code:=========================The U-Boot source code is maintained in the git repository atgit://www.denx.de/git/u-boot.git ; you can browse it online athttp://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summaryThe "snapshot" links on this page allow you to download tarballs ofany version you might be interested in. Official releases are alsoavailable for FTP download from the ftp://ftp.denx.de/pub/u-boot/directory.Pre-built (and tested) images are available fromftp://ftp.denx.de/pub/u-boot/images/Where we come from:===================- start from 8xxrom sources- create PPCBoot project (http://sourceforge.net/projects/ppcboot)- clean up code- make it easier to add custom boards- make it possible to add other [PowerPC] CPUs- extend functions, especially:  * Provide extended interface to Linux boot loader  * S-Record download  * network boot  * PCMCIA / CompactFlash / ATA disk / SCSI ... boot- create ARMBoot project (http://sourceforge.net/projects/armboot)- add other CPU families (starting with ARM)- create U-Boot project (http://sourceforge.net/projects/u-boot)- current project page: seehttp://www.denx.de/wiki/U-BootNames and Spelling:===================The "official" name of this project is "Das U-Boot". The spelling"U-Boot" shall be used in all written text (documentation, commentsin source files etc.). Example:This is the README file for the U-Boot project.File names etc. shall be based on the string "u-boot". Examples:include/asm-ppc/u-boot.h#include <asm/u-boot.h>Variable names, preprocessor constants etc. shall be either based onthe string "u_boot" or on "U_BOOT". Example:U_BOOT_VERSIONu_boot_logoIH_OS_U_BOOTu_boot_hush_startVersioning:===========Starting with the release in October 2008, the names of the releaseswere changed from numerical release numbers without deeper meaninginto a time stamp based numbering. Regular releases are identified bynames consisting of the calendar year and month of the release date.Additional fields (if present) indicate release candidates or bug fixreleases in "stable" maintenance trees.Examples:U-Boot v2009.11    - Release November 2009U-Boot v2009.11.1   - Release 1 in version November 2009 stable treeU-Boot v2010.09-rc1 - Release candiate 1 for September 2010 releaseDirectory Hierarchy:====================/archArchitecture specific files  /arcFiles generic to ARC architecture    /cpuCPU specific files      /arc700Files specific to ARC 700 CPUs    /libArchitecture specific library files  /armFiles generic to ARM architecture    /cpuCPU specific files      /arm720tFiles specific to ARM 720 CPUs      /arm920tFiles specific to ARM 920 CPUs/at91Files specific to Atmel AT91RM9200 CPU/imxFiles specific to Freescale MC9328 i.MX CPUs/s3c24x0Files specific to Samsung S3C24X0 CPUs      /arm926ejsFiles specific to ARM 926 CPUs      /arm1136Files specific to ARM 1136 CPUs      /pxaFiles specific to Intel XScale PXA CPUs      /sa1100Files specific to Intel StrongARM SA1100 CPUs    /libArchitecture specific library files  /avr32Files generic to AVR32 architecture    /cpuCPU specific files    /libArchitecture specific library files  /blackfinFiles generic to Analog Devices Blackfin architecture    /cpuCPU specific files    /libArchitecture specific library files  /m68kFiles generic to m68k architecture    /cpuCPU specific files      /mcf52x2Files specific to Freescale ColdFire MCF52x2 CPUs      /mcf5227xFiles specific to Freescale ColdFire MCF5227x CPUs      /mcf532xFiles specific to Freescale ColdFire MCF5329 CPUs      /mcf5445xFiles specific to Freescale ColdFire MCF5445x CPUs      /mcf547x_8xFiles specific to Freescale ColdFire MCF547x_8x CPUs    /libArchitecture specific library files  /microblazeFiles generic to microblaze architecture    /cpuCPU specific files    /libArchitecture specific library files  /mipsFiles generic to MIPS architecture    /cpuCPU specific files      /mips32Files specific to MIPS32 CPUs      /mips64Files specific to MIPS64 CPUs    /libArchitecture specific library files  /nds32Files generic to NDS32 architecture    /cpuCPU specific files      /n1213Files specific to Andes Technology N1213 CPUs    /libArchitecture specific library files  /nios2Files generic to Altera NIOS2 architecture    /cpuCPU specific files    /libArchitecture specific library files  /openriscFiles generic to OpenRISC architecture    /cpuCPU specific files    /libArchitecture specific library files  /powerpcFiles generic to PowerPC architecture    /cpuCPU specific files      /mpc5xxFiles specific to Freescale MPC5xx CPUs      /mpc5xxxFiles specific to Freescale MPC5xxx CPUs      /mpc8xxFiles specific to Freescale MPC8xx CPUs      /mpc8260Files specific to Freescale MPC8260 CPUs      /mpc85xxFiles specific to Freescale MPC85xx CPUs      /ppc4xxFiles specific to AMCC PowerPC 4xx CPUs    /libArchitecture specific library files  /shFiles generic to SH architecture    /cpuCPU specific files      /sh2Files specific to sh2 CPUs      /sh3Files specific to sh3 CPUs      /sh4Files specific to sh4 CPUs    /libArchitecture specific library files  /sparcFiles generic to SPARC architecture    /cpuCPU specific files      /leon2Files specific to Gaisler LEON2 SPARC CPU      /leon3Files specific to Gaisler LEON3 SPARC CPU    /libArchitecture specific library files  /x86Files generic to x86 architecture    /cpuCPU specific files    /libArchitecture specific library files/apiMachine/arch independent API for external apps/boardBoard dependent files/commonMisc architecture independent functions/diskCode for disk drive partition handling/docDocumentation (don't expect too much)/driversCommonly used device drivers/dtsContains Makefile for building internal U-Boot fdt./examplesExample code for standalone applications, etc./fsFilesystem code (cramfs, ext2, jffs2, etc.)/includeHeader Files/libFiles generic to all architectures  /libfdtLibrary files to support flattened device trees  /lzmaLibrary files to support LZMA decompression  /lzoLibrary files to support LZO decompression/netNetworking code/postPower On Self Test/splSecondary Program Loader framework/toolsTools to build S-Record or U-Boot images, etc.Software Configuration:=======================Configuration is usually done using C preprocessor defines; therationale behind that is to avoid dead code whenever possible.There are two classes of configuration variables:* Configuration _OPTIONS_:  These are selectable by the user and have names beginning with  "CONFIG_".* Configuration _SETTINGS_:  These depend on the hardware etc. and should not be meddled with if  you don't know what you're doing; they have names beginning with  "CONFIG_SYS_".Later we will add a configuration tool - probably similar to or evenidentical to what's used for the Linux kernel. Right now, we have todo the configuration by hand, which means creating some symboliclinks and editing some configuration files. We use the TQM8xxL boardsas an example here.Selection of Processor Architecture and Board Type:---------------------------------------------------For all supported boards there are ready-to-use defaultconfigurations available; just type "make <board_name>_defconfig".Example: For a TQM823L module type:cd u-bootmake TQM823L_defconfigFor the Cogent platform, you need to specify the CPU type as well;e.g. "make cogent_mpc8xx_defconfig". And also configure the cogentdirectory according to the instructions in cogent/README.Sandbox Environment:--------------------U-Boot can be built natively to run on a Linux host using the 'sandbox'board. This allows feature development which is not board- or architecture-specific to be undertaken on a native platform. The sandbox is also used torun some of U-Boot's tests.See board/sandbox/README.sandbox for more details.Board Initialisation Flow:--------------------------This is the intended start-up flow for boards. This should apply for bothSPL and U-Boot proper (i.e. they both follow the same rules). At present SPLmostly uses a separate code path, but the funtion names and roles of eachfunction are the same. Some boards or architectures may not conform to this.At least most ARM boards which use CONFIG_SPL_FRAMEWORK conform to this.Execution starts with start.S with three functions called during init afterthat. The purpose and limitations of each is described below.lowlevel_init():- purpose: essential init to permit execution to reach board_init_f()- no global_data or BSS- there is no stack (ARMv7 may have one but it will soon be removed)- must not set up SDRAM or use console- must only do the bare minimum to allow execution to continue toboard_init_f()- this is almost never needed- return normally from this functionboard_init_f():- purpose: set up the machine ready for running board_init_r():i.e. SDRAM and serial UART- global_data is available- stack is in SRAM- BSS is not available, so you cannot use global/static variables,only stack variables and global_dataNon-SPL-specific notes:- dram_init() is called to set up DRAM. If already done in SPL thiscan do nothingSPL-specific notes:- you can override the entire board_init_f() function with your ownversion as needed.- preloader_console_init() can be called here in extremis- should set up SDRAM, and anything needed to make the UART work- these is no need to clear BSS, it will be done by crt0.S- must return normally from this function (don't call board_init_r()directly)Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then atthis point the stack and global_data are relocated to belowCONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top ofmemory.board_init_r():- purpose: main execution, common code- global_data is available- SDRAM is available- BSS is available, all static/global variables can be used- execution eventually continues to main_loop()Non-SPL-specific notes:- U-Boot is relocated to the top of memory and is now running fromthere.SPL-specific notes:- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined andCONFIG_SPL_STACK_R_ADDR points into SDRAM- preloader_console_init() can be called here - typically this isdone by defining CONFIG_SPL_BOARD_INIT and then supplying aspl_board_init() function containing this call- loads U-Boot or (in falcon mode) LinuxConfiguration Options:----------------------Configuration depends on the combination of board and CPU type; allsuch information is kept in a configuration file"include/configs/<board_name>.h".Example: For a TQM823L module, all configuration settings are in"include/configs/TQM823L.h".Many of the options are named exactly as the corresponding Linuxkernel configuration options. The intention is to make it easier tobuild a config tool - later.The following options need to be configured:- CPU Type:Define exactly one, e.g. CONFIG_MPC85XX.- Board Type:Define exactly one, e.g. CONFIG_MPC8540ADS.- CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)Define exactly one, e.g. CONFIG_ATSTK1002- CPU Module Type: (if CONFIG_COGENT is defined)Define exactly one ofCONFIG_CMA286_60_OLD--- FIXME --- not tested yet:CONFIG_CMA286_60, CONFIG_CMA286_21, CONFIG_CMA286_60P,CONFIG_CMA287_23, CONFIG_CMA287_50- Motherboard Type: (if CONFIG_COGENT is defined)Define exactly one ofCONFIG_CMA101, CONFIG_CMA102- Motherboard I/O Modules: (if CONFIG_COGENT is defined)Define one or more ofCONFIG_CMA302- Motherboard Options: (if CONFIG_CMA101 or CONFIG_CMA102 are defined)Define one or more ofCONFIG_LCD_HEARTBEAT- update a character position on  the LCD display every second with  a "rotator" |\-/|\-/- Marvell Family MemberCONFIG_SYS_MVFS- define it if you want to enable  multiple fs option at one time  for marvell soc family- 8xx CPU Options: (if using an MPC8xx CPU)CONFIG_8xx_GCLK_FREQ- deprecated: CPU clock if  get_gclk_freq() cannot work  e.g. if there is no 32KHz  reference PIT/RTC clockCONFIG_8xx_OSCLK- PLL input clock (either EXTCLK  or XTAL/EXTAL)- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):CONFIG_SYS_8xx_CPUCLK_MINCONFIG_SYS_8xx_CPUCLK_MAXCONFIG_8xx_CPUCLK_DEFAULTSee doc/README.MPC866CONFIG_SYS_MEASURE_CPUCLKDefine this to measure the actual CPU clock insteadof relying on the correctness of the configuredvalues. Mostly useful for board bringup to make surethe PLL is locked at the intended frequency. Notethat this requires a (stable) reference clock (32 kHzRTC clock or CONFIG_SYS_8XX_XIN)CONFIG_SYS_DELAYED_ICACHEDefine this option if you want to enable theICache only when Code runs from RAM.- 85xx CPU Options:CONFIG_SYS_PPC64Specifies that the core is a 64-bit PowerPC implementation (implementsthe "64" category of the Power ISA). This is necessary for ePAPRcompliance, among other possible reasons.CONFIG_SYS_FSL_TBCLK_DIVDefines the core time base clock divider ratio compared to thesystem clock.  On most PQ3 devices this is 8, on newer QorIQdevices it can be 16 or 32.  The ratio varies from SoC to Soc.CONFIG_SYS_FSL_PCIE_COMPATDefines the string to utilize when trying to match PCIe devicetree nodes for the given platform.CONFIG_SYS_PPC_E500_DEBUG_TLBEnables a temporary TLB entry to be used during boot to workaround limitations in e500v1 and e500v2 external debuggersupport. This reduces the portions of the boot code wherebreakpoints and single stepping do not work.  The value of thissymbol should be set to the TLB1 entry to be used for thispurpose.CONFIG_SYS_FSL_ERRATUM_A004510Enables a workaround for erratum A004510.  If set,then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV andCONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REVCONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)Defines one or two SoC revisions (low 8 bits of SVR)for which the A004510 workaround should be applied.The rest of SVR is either not relevant to the decisionof whether the erratum is present (e.g. p2040 versusp2041) or is implied by the build target, which controlswhether CONFIG_SYS_FSL_ERRATUM_A004510 is set.See Freescale App Note 4493 for more information aboutthis erratum.CONFIG_A003399_NOR_WORKAROUNDEnables a workaround for IFC erratum A003399. It is onlyrequired during NOR boot.CONFIG_A008044_WORKAROUNDEnables a workaround for T1040/T1042 erratum A008044. It is onlyrequired during NAND boot and valid for Rev 1.0 SoC revisionCONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLYThis is the value to write into CCSR offset 0x18600according to the A004510 workaround.CONFIG_SYS_FSL_DSP_DDR_ADDRThis value denotes start offset of DDR memory which isconnected exclusively to the DSP cores.CONFIG_SYS_FSL_DSP_M2_RAM_ADDRThis value denotes start offset of M2 memorywhich is directly connected to the DSP core.CONFIG_SYS_FSL_DSP_M3_RAM_ADDRThis value denotes start offset of M3 memory which is directlyconnected to the DSP core.CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULTThis value denotes start offset of DSP CCSR space.CONFIG_SYS_FSL_SINGLE_SOURCE_CLKSingle Source Clock is clocking mode present in some of FSL SoC's.In this mode, a single differential clock is used to supplyclocks to the sysclock, ddrclock and usbclock.CONFIG_SYS_CPC_REINIT_FThis CONFIG is defined when the CPC is configured as SRAM at thetime of U-boot entry and is required to be re-initialized.CONFIG_DEEP_SLEEPIndicates this SoC supports deep sleep feature. If deep sleep issupported, core will start to execute uboot when wakes up.- Generic CPU options:CONFIG_SYS_GENERIC_GLOBAL_DATADefines global data is initialized in generic board board_init_f().If this macro is defined, global data is created and cleared ingeneric board board_init_f(). Without this macro, architecture/boardshould initialize global data before calling board_init_f().CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIANDefines the endianess of the CPU. Implementation of thosevalues is arch specific.CONFIG_SYS_FSL_DDRFreescale DDR driver in use. This type of DDR controller isfound in mpc83xx, mpc85xx, mpc86xx as well as some ARM coreSoCs.CONFIG_SYS_FSL_DDR_ADDRFreescale DDR memory-mapped register base.CONFIG_SYS_FSL_DDR_EMUSpecify emulator support for DDR. Some DDR features such asdeskew training are not available.CONFIG_SYS_FSL_DDRC_GEN1Freescale DDR1 controller.CONFIG_SYS_FSL_DDRC_GEN2Freescale DDR2 controller.CONFIG_SYS_FSL_DDRC_GEN3Freescale DDR3 controller.CONFIG_SYS_FSL_DDRC_GEN4Freescale DDR4 controller.CONFIG_SYS_FSL_DDRC_ARM_GEN3Freescale DDR3 controller for ARM-based SoCs.CONFIG_SYS_FSL_DDR1Board config to use DDR1. It can be enabled for SoCs withFreescale DDR1 or DDR2 controllers, depending on the boardimplemetation.CONFIG_SYS_FSL_DDR2Board config to use DDR2. It can be eanbeld for SoCs withFreescale DDR2 or DDR3 controllers, depending on the boardimplementation.CONFIG_SYS_FSL_DDR3Board config to use DDR3. It can be enabled for SoCs withFreescale DDR3 or DDR3L controllers.CONFIG_SYS_FSL_DDR3LBoard config to use DDR3L. It can be enabled for SoCs withDDR3L controllers.CONFIG_SYS_FSL_DDR4Board config to use DDR4. It can be enabled for SoCs withDDR4 controllers.CONFIG_SYS_FSL_IFC_BEDefines the IFC controller register space as Big EndianCONFIG_SYS_FSL_IFC_LEDefines the IFC controller register space as Little EndianCONFIG_SYS_FSL_PBL_PBIIt enables addition of RCW (Power on reset configuration) in built image.Please refer doc/README.pblimage for more detailsCONFIG_SYS_FSL_PBL_RCWIt adds PBI(pre-boot instructions) commands in u-boot build image.PBI commands can be used to configure SoC before it starts the execution.Please refer doc/README.pblimage for more detailsCONFIG_SPL_FSL_PBLIt adds a target to create boot binary having SPL binary in PBI formatconcatenated with u-boot binary.CONFIG_SYS_FSL_DDR_BEDefines the DDR controller register space as Big EndianCONFIG_SYS_FSL_DDR_LEDefines the DDR controller register space as Little EndianCONFIG_SYS_FSL_DDR_SDRAM_BASE_PHYPhysical address from the view of DDR controllers. It is thesame as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. Butit could be different for ARM SoCs.CONFIG_SYS_FSL_DDR_INTLV_256BDDR controller interleaving on 256-byte. This is a specialinterleaving mode, handled by Dickens for Freescale layerscapeSoCs with ARM core.CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLSNumber of controllers used as main memory.CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLSNumber of controllers used for other than main memory.CONFIG_SYS_FSL_HAS_DP_DDRDefines the SoC has DP-DDR used for DPAA.CONFIG_SYS_FSL_SEC_BEDefines the SEC controller register space as Big EndianCONFIG_SYS_FSL_SEC_LEDefines the SEC controller register space as Little Endian- Intel Monahans options:CONFIG_SYS_MONAHANS_RUN_MODE_OSC_RATIODefines the Monahans run mode to oscillatorratio. Valid values are 8, 16, 24, 31. The corefrequency is this value multiplied by 13 MHz.CONFIG_SYS_MONAHANS_TURBO_RUN_MODE_RATIODefines the Monahans turbo mode to oscillatorratio. Valid values are 1 (default if undefined) and2. The core frequency as calculated above is multipliedby this value.- MIPS CPU options:CONFIG_SYS_INIT_SP_OFFSETOffset relative to CONFIG_SYS_SDRAM_BASE for initial stackpointer. This is needed for the temporary stack beforerelocation.CONFIG_SYS_MIPS_CACHE_MODECache operation mode for the MIPS CPU.See also arch/mips/include/asm/mipsregs.h.Possible values are:CONF_CM_CACHABLE_NO_WACONF_CM_CACHABLE_WACONF_CM_UNCACHEDCONF_CM_CACHABLE_NONCOHERENTCONF_CM_CACHABLE_CECONF_CM_CACHABLE_COWCONF_CM_CACHABLE_CUWCONF_CM_CACHABLE_ACCELERATEDCONFIG_SYS_XWAY_EBU_BOOTCFGSpecial option for Lantiq XWAY SoCs for booting from NOR flash.See also arch/mips/cpu/mips32/start.S.CONFIG_XWAY_SWAP_BYTESEnable compilation of tools/xway-swap-bytes needed for LantiqXWAY SoCs for booting from NOR flash. The U-Boot image needs tobe swapped if a flash programmer is used.- ARM options:CONFIG_SYS_EXCEPTION_VECTORS_HIGHSelect high exception vectors of the ARM core, e.g., do notclear the V bit of the c1 register of CP15.CONFIG_SYS_THUMB_BUILDUse this flag to build U-Boot using the Thumb instructionset for ARM architectures. Thumb instruction set providesbetter code density. For ARM architectures that supportThumb2 this flag will result in Thumb2 code generated byGCC.CONFIG_ARM_ERRATA_716044CONFIG_ARM_ERRATA_742230CONFIG_ARM_ERRATA_743622CONFIG_ARM_ERRATA_751472CONFIG_ARM_ERRATA_761320CONFIG_ARM_ERRATA_773022CONFIG_ARM_ERRATA_774769CONFIG_ARM_ERRATA_794072If set, the workarounds for these ARM errata are applied earlyduring U-Boot startup. Note that these options force theworkarounds to be applied; no CPU-type/version detectionexists, unlike the similar options in the Linux kernel. Do notset these options unless they apply!COUNTER_FREQUENCYGeneric timer clock source frequency.COUNTER_FREQUENCY_REALGeneric timer clock source frequency if the real clock isdifferent from COUNTER_FREQUENCY, and can only be determinedat run time.NOTE: The following can be machine specific errata. Thesedo have ability to provide rudimentary version and machinespecific checks, but expect no product checks.CONFIG_ARM_ERRATA_430973CONFIG_ARM_ERRATA_454179CONFIG_ARM_ERRATA_621766CONFIG_ARM_ERRATA_798870CONFIG_ARM_ERRATA_801819- Tegra SoC options:CONFIG_TEGRA_SUPPORT_NON_SECURESupport executing U-Boot in non-secure (NS) mode. Certainimpossible actions will be skipped if the CPU is in NS mode,such as ARM architectural timer initialization.- Linux Kernel Interface:CONFIG_CLOCKS_IN_MHZU-Boot stores all clock information in Hzinternally. For binary compatibility with older Linuxkernels (which expect the clocks passed in thebd_info data to be in MHz) the environment variable"clocks_in_mhz" can be defined so that U-Bootconverts clock data to MHZ before passing it to theLinux kernel.When CONFIG_CLOCKS_IN_MHZ is defined, a definition of"clocks_in_mhz=1" is automatically included in thedefault environment.CONFIG_MEMSIZE_IN_BYTES[relevant for MIPS only]When transferring memsize parameter to Linux, some versionsexpect it to be in bytes, others in MB.Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.CONFIG_OF_LIBFDTNew kernel versions are expecting firmware settings to bepassed using flattened device trees (based on open firmwareconcepts).CONFIG_OF_LIBFDT * New libfdt-based support * Adds the "fdt" command * The bootm command automatically updates the fdtOF_CPU - The proper name of the cpus node (only required forMPC512X and MPC5xxx based boards).OF_SOC - The proper name of the soc node (only required forMPC512X and MPC5xxx based boards).OF_TBCLK - The timebase frequency.OF_STDOUT_PATH - The path to the console deviceboards with QUICC Engines require OF_QE to set UCC MACaddressesCONFIG_OF_BOARD_SETUPBoard code has addition modification that it wants to maketo the flat device tree before handing it off to the kernelCONFIG_OF_SYSTEM_SETUPOther code has addition modification that it wants to maketo the flat device tree before handing it off to the kernel.This causes ft_system_setup() to be called before bootingthe kernel.CONFIG_OF_BOOT_CPUThis define fills in the correct boot CPU in the bootparam header, the default value is zero if undefined.CONFIG_OF_IDE_FIXUPU-Boot can detect if an IDE device is present or not.If not, and this new config option is activated, U-Bootremoves the ATA node from the DTS before booting Linux,so the Linux IDE driver does not probe the device andcrash. This is needed for buggy hardware (uc101) whereno pull down resistor is connected to the signal IDE5V_DD7.CONFIG_MACH_TYPE[relevant for ARM only][mandatory]This setting is mandatory for all boards that have only onemachine type and must be used to specify the machine typenumber as it appears in the ARM machine registry(seehttp://www.arm.linux.org.uk/developer/machines/).Only boards that have multiple machine types supportedin a single configuration file and the machine type isruntime discoverable, do not have to use this setting.- vxWorks boot parameters:bootvx constructs a valid bootline using the followingenvironments variables: bootdev, bootfile, ipaddr, netmask,serverip, gatewayip, hostname, othbootargs.It loads the vxWorks image pointed bootfile.Note: If a "bootargs" environment is defined, it will overwridethe defaults discussed just above.- Cache Configuration:CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-BootCONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-BootCONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot- Cache Configuration for ARM:CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache      controllerCONFIG_SYS_PL310_BASE - Physical base address of PL310controller register space- Serial Ports:CONFIG_PL010_SERIALDefine this if you want support for Amba PrimeCell PL010 UARTs.CONFIG_PL011_SERIALDefine this if you want support for Amba PrimeCell PL011 UARTs.CONFIG_PL011_CLOCKIf you have Amba PrimeCell PL011 UARTs, set this variable tothe clock speed of the UARTs.CONFIG_PL01x_PORTSIf you have Amba PrimeCell PL010 or PL011 UARTs on your board,define this to a list of base addresses for each (supported)port. See e.g. include/configs/versatile.hCONFIG_SERIAL_HW_FLOW_CONTROLDefine this variable to enable hw flow control in serial driver.Current user of this option is drivers/serial/nsl16550.c driver- Console Interface:Depending on board, define exactly one serial port(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,CONFIG_8xx_CONS_SCC1, ...), or switch off the serialconsole by defining CONFIG_8xx_CONS_NONENote: if CONFIG_8xx_CONS_NONE is defined, the serialport routines must be defined elsewhere(i.e. serial_init(), serial_getc(), ...)CONFIG_CFB_CONSOLEEnables console device for a color framebuffer. Needs followingdefines (cf. smiLynxEM, i8042)VIDEO_FB_LITTLE_ENDIANgraphic memory organisation(default big endian)VIDEO_HW_RECTFILLgraphic chip supportsrectangle fill(cf. smiLynxEM)VIDEO_HW_BITBLTgraphic chip supportsbit-blit (cf. smiLynxEM)VIDEO_VISIBLE_COLSvisible pixel columns(cols=pitch)VIDEO_VISIBLE_ROWSvisible pixel rowsVIDEO_PIXEL_SIZEbytes per pixelVIDEO_DATA_FORMATgraphic data format(0-5, cf. cfb_console.c)VIDEO_FB_ADRSframebuffer addressVIDEO_KBD_INIT_FCTkeyboard int fct(i.e. rx51_kp_init())VIDEO_TSTC_FCTtest char fct(i.e. rx51_kp_tstc)VIDEO_GETC_FCTget char fct(i.e. rx51_kp_getc)CONFIG_VIDEO_LOGOdisplay Linux logo inupper left cornerCONFIG_VIDEO_BMP_LOGOuse bmp_logo.h instead oflinux_logo.h for logo.Requires CONFIG_VIDEO_LOGOCONFIG_CONSOLE_EXTRA_INFOadditional board info besidethe logoWhen CONFIG_CFB_CONSOLE_ANSI is defined, console will supporta limited number of ANSI escape sequences (cursor control,erase functions and limited graphics rendition control).When CONFIG_CFB_CONSOLE is defined, video console isdefault i/o. Serial console can be forced withenvironment 'console=serial'.When CONFIG_SILENT_CONSOLE is defined, all consolemessages (by U-Boot and Linux!) can be silenced withthe "silent" environment variable. Seedoc/README.silent for more information.CONFIG_SYS_CONSOLE_BG_COL: define the backgroundcolor, defaultis 0x00.CONFIG_SYS_CONSOLE_FG_COL: define the foregroundcolor, defaultis 0xa0.- Console Baudrate:CONFIG_BAUDRATE - in bpsSelect one of the baudrates listed inCONFIG_SYS_BAUDRATE_TABLE, see below.CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale- Console Rx buffer lengthWith CONFIG_SYS_SMC_RXBUFLEN it is possible to definethe maximum receive buffer length for the SMC.This option is actual only for 82xx and 8xx possible.If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLEmust be defined, to setup the maximum idle timeout forthe SMC.- Pre-Console Buffer:Prior to the console being initialised (i.e. serial UARTinitialised etc) all console output is silently discarded.Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot tobuffer any console messages prior to the console beinginitialised to a buffer of size CONFIG_PRE_CON_BUF_SZbytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer isa circular buffer, so if more than CONFIG_PRE_CON_BUF_SZbytes are output before the console is initialised, theearlier bytes are discarded.Note that when printing the buffer a copy is made on thestack so CONFIG_PRE_CON_BUF_SZ must fit on the stack.'Sane' compilers will generate smaller code ifCONFIG_PRE_CON_BUF_SZ is a power of 2- Safe printf() functionsDefine CONFIG_SYS_VSNPRINTF to compile in safe versions ofthe printf() functions. These are defined ininclude/vsprintf.h and include snprintf(), vsnprintf() andso on. Code size increase is approximately 300-500 bytes.If this option is not given then these functions willsilently discard their buffer size argument - this meansyou are not getting any overflow checking in this case.- Boot Delay:CONFIG_BOOTDELAY - in secondsDelay before automatically booting the default image;set to -1 to disable autoboot.set to -2 to autoboot with no delay and not check for abort(even when CONFIG_ZERO_BOOTDELAY_CHECK is defined).See doc/README.autoboot for these options thatwork with CONFIG_BOOTDELAY. None are required.CONFIG_BOOT_RETRY_TIMECONFIG_BOOT_RETRY_MINCONFIG_AUTOBOOT_KEYEDCONFIG_AUTOBOOT_PROMPTCONFIG_AUTOBOOT_DELAY_STRCONFIG_AUTOBOOT_STOP_STRCONFIG_ZERO_BOOTDELAY_CHECKCONFIG_RESET_TO_RETRY- Autoboot Command:CONFIG_BOOTCOMMANDOnly needed when CONFIG_BOOTDELAY is enabled;define a command string that is automatically executedwhen no character is read on the console interfacewithin "Boot Delay" after reset.CONFIG_BOOTARGSThis can be used to pass arguments to the bootmcommand. The value of CONFIG_BOOTARGS goes into theenvironment value "bootargs".CONFIG_RAMBOOT and CONFIG_NFSBOOTThe value of these goes into the environment as"ramboot" and "nfsboot" respectively, and can be usedas a convenience, when switching between booting fromRAM and NFS.- Bootcount:CONFIG_BOOTCOUNT_LIMITImplements a mechanism for detecting a repeating rebootcycle, see:http://www.denx.de/wiki/view/DULG/UBootBootCountLimitCONFIG_BOOTCOUNT_ENVIf no softreset save registers are found on the hardware"bootcount" is stored in the environment. To prevent asaveenv on all reboots, the environment variable"upgrade_available" is used. If "upgrade_available" is0, "bootcount" is always 0, if "upgrade_available" is1 "bootcount" is incremented in the environment.So the Userspace Applikation must set the "upgrade_available"and "bootcount" variable to 0, if a boot was successfully.- Pre-Boot Commands:CONFIG_PREBOOTWhen this option is #defined, the existence of theenvironment variable "preboot" will be checkedimmediately before starting the CONFIG_BOOTDELAYcountdown and/or running the auto-boot command resp.entering interactive mode.This feature is especially useful when "preboot" isautomatically generated or modified. For an examplesee the LWMON board specific code: here "preboot" ismodified when the user holds down a certaincombination of keys on the (special) keyboard whenbooting the systems- Serial Download Echo Mode:CONFIG_LOADS_ECHOIf defined to 1, all characters received during aserial download (using the "loads" command) areechoed back. This might be needed by some terminalemulations (like "cu"), but may as well just taketime on others. This setting #define's the initialvalue of the "loads_echo" environment variable.- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)CONFIG_KGDB_BAUDRATESelect one of the baudrates listed inCONFIG_SYS_BAUDRATE_TABLE, see below.- Monitor Functions:Monitor commands can be included or excludedfrom the build by using the #include files<config_cmd_all.h> and #undef'ing unwantedcommands, or adding #define's for wanted commands.The default command configuration includes all commandsexcept those marked below with a "*".CONFIG_CMD_AES  AES 128 CBC encrypt/decryptCONFIG_CMD_ASKENV* ask for env variableCONFIG_CMD_BDI  bdinfoCONFIG_CMD_BEDBUG* Include BedBug DebuggerCONFIG_CMD_BMP* BMP supportCONFIG_CMD_BSP* Board specific commandsCONFIG_CMD_BOOTD  bootdCONFIG_CMD_BOOTI* ARM64 Linux kernel Image supportCONFIG_CMD_CACHE* icache, dcacheCONFIG_CMD_CLK   * clock command supportCONFIG_CMD_CONSOLE  coninfoCONFIG_CMD_CRC32* crc32CONFIG_CMD_DATE* support for RTC, date/time...CONFIG_CMD_DHCP* DHCP supportCONFIG_CMD_DIAG* DiagnosticsCONFIG_CMD_DS4510* ds4510 I2C gpio commandsCONFIG_CMD_DS4510_INFO* ds4510 I2C info commandCONFIG_CMD_DS4510_MEM* ds4510 I2C eeprom/sram commansdCONFIG_CMD_DS4510_RST* ds4510 I2C rst commandCONFIG_CMD_DTT* Digital Therm and ThermostatCONFIG_CMD_ECHO  echo argumentsCONFIG_CMD_EDITENV  edit env variableCONFIG_CMD_EEPROM* EEPROM read/write supportCONFIG_CMD_ELF* bootelf, bootvxCONFIG_CMD_ENV_CALLBACK* display details about env callbacksCONFIG_CMD_ENV_FLAGS* display details about env flagsCONFIG_CMD_ENV_EXISTS* check existence of env variableCONFIG_CMD_EXPORTENV* export the environmentCONFIG_CMD_EXT2* ext2 command supportCONFIG_CMD_EXT4* ext4 command supportCONFIG_CMD_FS_GENERIC* filesystem commands (e.g. load, ls)  that work for multiple fs typesCONFIG_CMD_FS_UUID* Look up a filesystem UUIDCONFIG_CMD_SAVEENV  saveenvCONFIG_CMD_FDC* Floppy Disk SupportCONFIG_CMD_FAT* FAT command supportCONFIG_CMD_FLASH  flinfo, erase, protectCONFIG_CMD_FPGA  FPGA device initialization supportCONFIG_CMD_FUSE* Device fuse supportCONFIG_CMD_GETTIME* Get time since bootCONFIG_CMD_GO* the 'go' command (exec code)CONFIG_CMD_GREPENV* search environmentCONFIG_CMD_HASH* calculate hash / digestCONFIG_CMD_HWFLOW* RTS/CTS hw flow controlCONFIG_CMD_I2C* I2C serial bus supportCONFIG_CMD_IDE* IDE harddisk supportCONFIG_CMD_IMI  iminfoCONFIG_CMD_IMLS  List all images found in NOR flashCONFIG_CMD_IMLS_NAND* List all images found in NAND flashCONFIG_CMD_IMMAP* IMMR dump supportCONFIG_CMD_IOTRACE* I/O tracing for debuggingCONFIG_CMD_IMPORTENV* import an environmentCONFIG_CMD_INI* import data from an ini file into the envCONFIG_CMD_IRQ* irqinfoCONFIG_CMD_ITEST  Integer/string test of 2 valuesCONFIG_CMD_JFFS2* JFFS2 SupportCONFIG_CMD_KGDB* kgdbCONFIG_CMD_LDRINFO* ldrinfo (display Blackfin loader)CONFIG_CMD_LINK_LOCAL* link-local IP address auto-configuration  (169.254.*.*)CONFIG_CMD_LOADB  loadbCONFIG_CMD_LOADS  loadsCONFIG_CMD_MD5SUM* print md5 message digest  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)CONFIG_CMD_MEMINFO* Display detailed memory informationCONFIG_CMD_MEMORY  md, mm, nm, mw, cp, cmp, crc, base,  loop, loopwCONFIG_CMD_MEMTEST* mtestCONFIG_CMD_MISC  Misc functions like sleep etcCONFIG_CMD_MMC* MMC memory mapped supportCONFIG_CMD_MII* MII utility commandsCONFIG_CMD_MTDPARTS* MTD partition supportCONFIG_CMD_NAND* NAND supportCONFIG_CMD_NET  bootp, tftpboot, rarpbootCONFIG_CMD_NFS  NFS supportCONFIG_CMD_PCA953X* PCA953x I2C gpio commandsCONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info commandCONFIG_CMD_PCI* pciinfoCONFIG_CMD_PCMCIA* PCMCIA supportCONFIG_CMD_PING* send ICMP ECHO_REQUEST to network  hostCONFIG_CMD_PORTIO* Port I/OCONFIG_CMD_READ* Read raw data from partitionCONFIG_CMD_REGINFO* Register dumpCONFIG_CMD_RUN  run command in env variableCONFIG_CMD_SANDBOX* sb command to access sandbox featuresCONFIG_CMD_SAVES* save S record dumpCONFIG_CMD_SCSI* SCSI SupportCONFIG_CMD_SDRAM* print SDRAM configuration information  (requires CONFIG_CMD_I2C)CONFIG_CMD_SETGETDCR  Support for DCR Register access  (4xx only)CONFIG_CMD_SF* Read/write/erase SPI NOR flashCONFIG_CMD_SHA1SUM* print sha1 memory digest  (requires CONFIG_CMD_MEMORY)CONFIG_CMD_SOFTSWITCH* Soft switch setting command for BF60xCONFIG_CMD_SOURCE  "source" command SupportCONFIG_CMD_SPI* SPI serial bus supportCONFIG_CMD_TFTPSRV* TFTP transfer in server modeCONFIG_CMD_TFTPPUT* TFTP put command (upload)CONFIG_CMD_TIME* run command and report execution time (ARM specific)CONFIG_CMD_TIMER* access to the system tick timerCONFIG_CMD_USB* USB supportCONFIG_CMD_CDP* Cisco Discover Protocol supportCONFIG_CMD_MFSL* Microblaze FSL supportCONFIG_CMD_XIMG  Load part of Multi ImageCONFIG_CMD_UUID* Generate random UUID or GUID stringEXAMPLE: If you want all functions except of networksupport you can write:#include "config_cmd_all.h"#undef CONFIG_CMD_NETOther Commands:fdt (flattened device tree) command: CONFIG_OF_LIBFDTNote:Don't enable the "icache" and "dcache" commands(configuration option CONFIG_CMD_CACHE) unless you knowwhat you (and your U-Boot users) are doing. Datacache cannot be enabled on systems like the 8xx or8260 (where accesses to the IMMR region must beuncached), and it cannot be disabled on all othersystems where we (mis-) use the data cache to hold aninitial stack and some data.XXX - this list needs to get updated!- Regular expression support:CONFIG_REGEXIf this variable is defined, U-Boot is linked againstthe SLRE (Super Light Regular Expression) library,which adds regex support to some commands, as forexample "env grep" and "setexpr".- Device tree:CONFIG_OF_CONTROLIf this variable is defined, U-Boot will use a device treeto configure its devices, instead of relying on staticallycompiled #defines in the board file. This option isexperimental and only available on a few boards. The devicetree is available in the global data as gd->fdt_blob.U-Boot needs to get its device tree from somewhere. This canbe done using one of the two options below:CONFIG_OF_EMBEDIf this variable is defined, U-Boot will embed a device treebinary in its image. This device tree file should be in theboard directory and called <soc>-<board>.dts. The binary fileis then picked up in board_init_f() and made available throughthe global data structure as gd->blob.CONFIG_OF_SEPARATEIf this variable is defined, U-Boot will build a device treebinary. It will be called u-boot.dtb. Architecture-specificcode will locate it at run-time. Generally this works by:cat u-boot.bin u-boot.dtb >image.binand in fact, U-Boot does this for you, creating a file calledu-boot-dtb.bin which is useful in the common case. You canstill use the individual files if you need something moreexotic.- Watchdog:CONFIG_WATCHDOGIf this variable is defined, it enables watchdogsupport for the SoC. There must be support in the SoCspecific code for a watchdog. For the 8xx and 8260CPUs, the SIU Watchdog feature is enabled in the SYPCRregister.  When supported for a specific SoC isavailable, then no further board specific code shouldbe needed to use it.CONFIG_HW_WATCHDOGWhen using a watchdog circuitry external to the usedSoC, then define this variable and provide boardspecific code for the "hw_watchdog_reset" function.CONFIG_AT91_HW_WDT_TIMEOUTspecify the timeout in seconds. default 2 seconds.- U-Boot Version:CONFIG_VERSION_VARIABLEIf this variable is defined, an environment variablenamed "ver" is created by U-Boot showing the U-Bootversion as printed by the "version" command.Any change to this variable will be reverted at thenext reset.- Real-Time Clock:When CONFIG_CMD_DATE is selected, the type of the RTChas to be selected, too. Define exactly one of thefollowing options:CONFIG_RTC_MPC8xx- use internal RTC of MPC8xxCONFIG_RTC_PCF8563- use Philips PCF8563 RTCCONFIG_RTC_MC13XXX- use MC13783 or MC13892 RTCCONFIG_RTC_MC146818- use MC146818 RTCCONFIG_RTC_DS1307- use Maxim, Inc. DS1307 RTCCONFIG_RTC_DS1337- use Maxim, Inc. DS1337 RTCCONFIG_RTC_DS1338- use Maxim, Inc. DS1338 RTCCONFIG_RTC_DS1339- use Maxim, Inc. DS1339 RTCCONFIG_RTC_DS164x- use Dallas DS164x RTCCONFIG_RTC_ISL1208- use Intersil ISL1208 RTCCONFIG_RTC_MAX6900- use Maxim, Inc. MAX6900 RTCCONFIG_SYS_RTC_DS1337_NOOSC- Turn off the OSC output for DS1337CONFIG_SYS_RV3029_TCR- enable trickle charger on  RV3029 RTC.Note that if the RTC uses I2C, then the I2C interfacemust also be configured. See I2C Support, below.- GPIO Support:CONFIG_PCA953X- use NXP's PCA953X series I2C GPIOThe CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list ofchip-ngpio pairs that tell the PCA953X driver the number ofpins supported by a particular chip.Note that if the GPIO device uses I2C, then the I2C interfacemust also be configured. See I2C Support, below.- I/O tracing:When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/Oaccesses and can checksum them or write a list of them outto memory. See the 'iotrace' command for details. This isuseful for testing device drivers since it can confirm thatthe driver behaves the same way before and after a codechange. Currently this is supported on sandbox and arm. Toadd support for your architecture, add '#include <iotrace.h>'to the bottom of arch/<arch>/include/asm/io.h and test.Example output from the 'iotrace stats' command is below.Note that if the trace buffer is exhausted, the checksum willstill continue to operate.iotrace is enabledStart:  10000000(buffer start address)Size:   00010000(buffer size)Offset: 00000120(current buffer offset)Output: 10000120(start + offset)Count:  00000018(number of trace records)CRC32:  9526fb66(CRC32 of all trace records)- Timestamp Support:When CONFIG_TIMESTAMP is selected, the timestamp(date and time) of an image is printed by imagecommands like bootm or iminfo. This option isautomatically enabled when you select CONFIG_CMD_DATE .- Partition Labels (disklabels) Supported:Zero or more of the following:CONFIG_MAC_PARTITION   Apple's MacOS partition table.CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the       Intel architecture, USB sticks, etc.CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the       bootloader.  Note 2TB partition limit; see       disk/part_efi.cCONFIG_MTD_PARTITIONS  Memory Technology Device partition table.If IDE or SCSI support is enabled (CONFIG_CMD_IDE orCONFIG_CMD_SCSI) you must configure support for atleast one non-MTD partition type as well.- IDE Reset method:CONFIG_IDE_RESET_ROUTINE - this is defined in severalboard configurations files but used nowhere!CONFIG_IDE_RESET - is this is defined, IDE Reset willbe performed by calling the functionide_set_reset(int reset)which has to be defined in a board specific file- ATAPI Support:CONFIG_ATAPISet this to enable ATAPI support.- LBA48 SupportCONFIG_LBA48Set this to enable support for disks larger than 137GBAlso look at CONFIG_SYS_64BIT_LBA.Whithout these , LBA48 support uses 32bit variables and will 'only'support disks up to 2.1TB.CONFIG_SYS_64BIT_LBA:When enabled, makes the IDE subsystem use 64bit sector addresses.Default is 32bit.- SCSI Support:At the moment only there is only support for theSYM53C8XX SCSI controller; defineCONFIG_SCSI_SYM53C8XX to enable it.CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] andCONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define themaximum numbers of LUNs, SCSI ID's and targetdevices.CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)The environment variable 'scsidevs' is set to the number ofSCSI devices found during the last scan.- NETWORK Support (PCI):CONFIG_E1000Support for Intel 8254x/8257x gigabit chips.CONFIG_E1000_SPIUtility code for direct access to the SPI bus on Intel 8257x.This does not do anything useful unless you set at least oneof CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.CONFIG_E1000_SPI_GENERICAllow generic access to the SPI bus on the Intel 8257x, forexample with the "sspi" command.CONFIG_CMD_E1000Management command for E1000 devices.  When used on deviceswith SPI support you can reprogram the EEPROM from U-Boot.CONFIG_EEPRO100Support for Intel 82557/82559/82559ER chips.Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROMwrite routine for first time initialisation.CONFIG_TULIPSupport for Digital 2114x chips.Optional CONFIG_TULIP_SELECT_MEDIA for board specificmodem chip initialisation (KS8761/QS6611).CONFIG_NATSEMISupport for National dp83815 chips.CONFIG_NS8382XSupport for National dp8382[01] gigabit chips.- NETWORK Support (other):CONFIG_DRIVER_AT91EMACSupport for AT91RM9200 EMAC.CONFIG_RMIIDefine this to use reduced MII intefaceCONFIG_DRIVER_AT91EMAC_QUIETIf this defined, the driver is quiet.The driver doen't show link status messages.CONFIG_CALXEDA_XGMACSupport for the Calxeda XGMAC deviceCONFIG_LAN91C96Support for SMSC's LAN91C96 chips.CONFIG_LAN91C96_BASEDefine this to hold the physical addressof the LAN91C96's I/O spaceCONFIG_LAN91C96_USE_32_BITDefine this to enable 32 bit addressingCONFIG_SMC91111Support for SMSC's LAN91C111 chipCONFIG_SMC91111_BASEDefine this to hold the physical addressof the device (I/O space)CONFIG_SMC_USE_32_BITDefine this if data bus is 32 bitsCONFIG_SMC_USE_IOFUNCSDefine this to use i/o functions instead of macros(some hardware wont work with macros)CONFIG_DRIVER_TI_EMACSupport for davinci emacCONFIG_SYS_DAVINCI_EMAC_PHY_COUNTDefine this if you have more then 3 PHYs.CONFIG_FTGMAC100Support for Faraday's FTGMAC100 Gigabit SoC EthernetCONFIG_FTGMAC100_EGIGADefine this to use GE link update with gigabit PHY.Define this if FTGMAC100 is connected to gigabit PHY.If your system has 10/100 PHY only, it might not occurwrong behavior. Because PHY usually return timeout oruseless data when polling gigabit status and gigabitcontrol registers. This behavior won't affect thecorrectnessof 10/100 link speed update.CONFIG_SMC911XSupport for SMSC's LAN911x and LAN921x chipsCONFIG_SMC911X_BASEDefine this to hold the physical addressof the device (I/O space)CONFIG_SMC911X_32_BITDefine this if data bus is 32 bitsCONFIG_SMC911X_16_BITDefine this if data bus is 16 bits. If your processorautomatically converts one 32 bit word to two 16 bitwords you may also try CONFIG_SMC911X_32_BIT.CONFIG_SH_ETHERSupport for Renesas on-chip Ethernet controllerCONFIG_SH_ETHER_USE_PORTDefine the number of ports to be usedCONFIG_SH_ETHER_PHY_ADDRDefine the ETH PHY's addressCONFIG_SH_ETHER_CACHE_WRITEBACKIf this option is set, the driver enables cache flush.- PWM Support:CONFIG_PWM_IMXSupport for PWM modul on the imx6.- TPM Support:CONFIG_TPMSupport TPM devices.CONFIG_TPM_TIS_INFINEONSupport for Infineon i2c bus TPM devices. Only one deviceper system is supported at this time.CONFIG_TPM_TIS_I2C_BURST_LIMITATIONDefine the burst count bytes upper limitCONFIG_TPM_ATMEL_TWISupport for Atmel TWI TPM device. Requires I2C support.CONFIG_TPM_TIS_LPCSupport for generic parallel port TPM devices. Only one deviceper system is supported at this time.CONFIG_TPM_TIS_BASE_ADDRESSBase address where the generic TPM device is mappedto. Contemporary x86 systems usually map it at0xfed40000.CONFIG_CMD_TPMAdd tpm monitor functions.Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, alsoprovides monitor access to authorized functions.CONFIG_TPMDefine this to enable the TPM support library which providesfunctional interfaces to some TPM commands.Requires support for a TPM device.CONFIG_TPM_AUTH_SESSIONSDefine this to enable authorized functions in the TPM library.Requires CONFIG_TPM and CONFIG_SHA1.- USB Support:At the moment only the UHCI host controller issupported (PIP405, MIP405, MPC5200); defineCONFIG_USB_UHCI to enable it.define CONFIG_USB_KEYBOARD to enable the USB Keyboardand define CONFIG_USB_STORAGE to enable the USBstorage devices.Note:Supported are USB Keyboards and USB Floppy drives(TEAC FD-05PUB).MPC5200 USB requires additional defines:CONFIG_USB_CLOCKfor 528 MHz Clock: 0x0001bbbbCONFIG_PSC3_USBfor USB on PSC3CONFIG_USB_CONFIGfor differential drivers: 0x00001000for single ended drivers: 0x00005000for differential drivers on PSC3: 0x00000100for single ended drivers on PSC3: 0x00004100CONFIG_SYS_USB_EVENT_POLLMay be defined to allow interrupt pollinginstead of using asynchronous interruptsCONFIG_USB_EHCI_TXFIFO_THRESH enables setting of thetxfilltuning field in the EHCI controller on reset.CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2HW module registers.- USB Device:Define the below if you wish to use the USB console.Once firmware is rebuilt from a serial console issue thecommand "setenv stdin usbtty; setenv stdout usbtty" andattach your USB cable. The Unix command "dmesg" should printit has found a new device. The environment variable usbttycan be set to gserial or cdc_acm to enable your device toappear to a USB host as a Linux gserial device or aCommon Device Class Abstract Control Model serial device.If you select usbtty = gserial you should be able to enumeratea Linux host by# modprobe usbserial vendor=0xVendorID product=0xProductIDelse if using cdc_acm, simply setting the environmentvariable usbtty to be cdc_acm should suffice. The followingmight be defined in YourBoardName.hCONFIG_USB_DEVICEDefine this to build a UDC deviceCONFIG_USB_TTYDefine this to have a tty type of device available totalk to the UDC deviceCONFIG_USBD_HSDefine this to enable the high speed support for usbdevice and usbtty. If this feature is enabled, a routineint is_usbd_high_speed(void)also needs to be defined by the driver to dynamically pollwhether the enumeration has succeded at high speed or fullspeed.CONFIG_SYS_CONSOLE_IS_IN_ENVDefine this if you want stdin, stdout &/or stderr tobe set to usbtty.mpc8xx:CONFIG_SYS_USB_EXTC_CLK 0xBLAHDerive USB clock from external clock "blah"- CONFIG_SYS_USB_EXTC_CLK 0x02CONFIG_SYS_USB_BRG_CLK 0xBLAHDerive USB clock from brgclk- CONFIG_SYS_USB_BRG_CLK 0x04If you have a USB-IF assigned VendorID then you may wish todefine your own vendor specific values either in BoardName.hor directly in usbd_vendor_info.h. If you don't defineCONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Bootshould pretend to be a Linux device to it's target host.CONFIG_USBD_MANUFACTURERDefine this string as the name of your company for- CONFIG_USBD_MANUFACTURER "my company"CONFIG_USBD_PRODUCT_NAMEDefine this string as the name of your product- CONFIG_USBD_PRODUCT_NAME "acme usb device"CONFIG_USBD_VENDORIDDefine this as your assigned Vendor ID from the USBImplementors Forum. This *must* be a genuine Vendor IDto avoid polluting the USB namespace.- CONFIG_USBD_VENDORID 0xFFFFCONFIG_USBD_PRODUCTIDDefine this as the unique Product IDfor your device- CONFIG_USBD_PRODUCTID 0xFFFF- ULPI Layer Support:The ULPI (UTMI Low Pin (count) Interface) PHYs are supported viathe generic ULPI layer. The generic layer accesses the ULPI PHYvia the platform viewport, so you need both the genric layer andthe viewport enabled. Currently only Chipidea/ARC basedviewport is supported.To enable the ULPI layer support, define CONFIG_USB_ULPI andCONFIG_USB_ULPI_VIEWPORT in your board configuration file.If your ULPI phy needs a different reference clock than thestandard 24 MHz then you have to define CONFIG_ULPI_REF_CLK tothe appropriate value in Hz.- MMC Support:The MMC controller on the Intel PXA is supported. Toenable this define CONFIG_MMC. The MMC can beaccessed from the boot prompt by mapping the deviceto physical memory similar to flash. Command line isenabled with CONFIG_CMD_MMC. The MMC driver also works withthe FAT fs. This is enabled with CONFIG_CMD_FAT.CONFIG_SH_MMCIFSupport for Renesas on-chip MMCIF controllerCONFIG_SH_MMCIF_ADDRDefine the base address of MMCIF registersCONFIG_SH_MMCIF_CLKDefine the clock frequency for MMCIFCONFIG_GENERIC_MMCEnable the generic MMC driverCONFIG_SUPPORT_EMMC_BOOTEnable some additional features of the eMMC boot partitions.CONFIG_SUPPORT_EMMC_RPMBEnable the commands for reading, writing and programming thekey for the Replay Protection Memory Block partition in eMMC.- USB Device Firmware Update (DFU) class support:CONFIG_USB_FUNCTION_DFUThis enables the USB portion of the DFU USB classCONFIG_CMD_DFUThis enables the command "dfu" which is used to haveU-Boot create a DFU class device via USB.  This commandrequires that the "dfu_alt_info" environment variable beset and define the alt settings to expose to the host.CONFIG_DFU_MMCThis enables support for exposing (e)MMC devices via DFU.CONFIG_DFU_NANDThis enables support for exposing NAND devices via DFU.CONFIG_DFU_RAMThis enables support for exposing RAM via DFU.Note: DFU spec refer to non-volatile memory usage, butallow usages beyond the scope of spec - here RAM usage,one that would help mostly the developer.CONFIG_SYS_DFU_DATA_BUF_SIZEDfu transfer uses a buffer before writing data to theraw storage device. Make the size (in bytes) of this bufferconfigurable. The size of this buffer is also configurablethrough the "dfu_bufsiz" environment variable.CONFIG_SYS_DFU_MAX_FILE_SIZEWhen updating files rather than the raw storage device,we use a static buffer to copy the file into and then writethe buffer once we've been given the whole file.  Definethis to the maximum filesize (in bytes) for the buffer.Default is 4 MiB if undefined.DFU_DEFAULT_POLL_TIMEOUTPoll timeout [ms], is the timeout a device can send to thehost. The host must wait for this timeout before sendinga subsequent DFU_GET_STATUS request to the device.DFU_MANIFEST_POLL_TIMEOUTPoll timeout [ms], which the device sends to the host whenentering dfuMANIFEST state. Host waits this timeout, beforesending again an USB request to the device.- USB Device Android Fastboot support:CONFIG_USB_FUNCTION_FASTBOOTThis enables the USB part of the fastboot gadgetCONFIG_CMD_FASTBOOTThis enables the command "fastboot" which enables the Androidfastboot mode for the platform's USB device. Fastboot is a USBprotocol for downloading images, flashing and device controlused on Android devices.See doc/README.android-fastboot for more information.CONFIG_ANDROID_BOOT_IMAGEThis enables support for booting images which use the Androidimage format header.CONFIG_FASTBOOT_BUF_ADDRThe fastboot protocol requires a large memory buffer fordownloads. Define this to the starting RAM address to use fordownloaded images.CONFIG_FASTBOOT_BUF_SIZEThe fastboot protocol requires a large memory buffer fordownloads. This buffer should be as large as possible for aplatform. Define this to the size available RAM for fastboot.CONFIG_FASTBOOT_FLASHThe fastboot protocol includes a "flash" command for writingthe downloaded image to a non-volatile storage device. Definethis to enable the "fastboot flash" command.CONFIG_FASTBOOT_FLASH_MMC_DEVThe fastboot "flash" command requires additional informationregarding the non-volatile storage device. Define this tothe eMMC device that fastboot should use to store the image.CONFIG_FASTBOOT_GPT_NAMEThe fastboot "flash" command supports writing the downloadedimage to the Protective MBR and the Primary GUID PartitionTable. (Additionally, this downloaded image is post-processedto generate and write the Backup GUID Partition Table.)This occurs when the specified "partition name" on the"fastboot flash" command line matches this value.Default is GPT_ENTRY_NAME (currently "gpt") if undefined.- Journaling Flash filesystem support:CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,CONFIG_JFFS2_NAND_DEVDefine these for a default partition on a NAND deviceCONFIG_SYS_JFFS2_FIRST_SECTOR,CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKSDefine these for a default partition on a NOR deviceCONFIG_SYS_JFFS_CUSTOM_PARTDefine this to create an own partition. You have to provide afunction struct part_info* jffs2_part_info(int part_num)If you define only one JFFS2 partition you may also want to#define CONFIG_SYS_JFFS_SINGLE_PART1to disable the command chpart. This is the default when youhave not defined a custom partition- FAT(File Allocation Table) filesystem write function support:CONFIG_FAT_WRITEDefine this to enable support for saving memory data as afile in FAT formatted partition.This will also enable the command "fatwrite" enabling theuser to write files to FAT.CBFS (Coreboot Filesystem) supportCONFIG_CMD_CBFSDefine this to enable support for reading from a Corebootfilesystem. Available commands are cbfsinit, cbfsinfo, cbfslsand cbfsload.- FAT(File Allocation Table) filesystem cluster size:CONFIG_FS_FAT_MAX_CLUSTSIZEDefine the max cluster size for fat operations elsea default value of 65536 will be defined.- Keyboard Support:See Kconfig help for available keyboard drivers.CONFIG_KEYBOARDDefine this to enable a custom keyboard support.This simply calls drv_keyboard_init() which must bedefined in your board-specific files. This option is deprecatedand is only used by novena. For new boards, use driver modelinstead.- Video support:CONFIG_VIDEODefine this to enable video support (for output tovideo).CONFIG_VIDEO_CT69000Enable Chips & Technologies 69000 Video chipCONFIG_VIDEO_SMI_LYNXEMEnable Silicon Motion SMI 712/710/810 Video chip. Thevideo output is selected via environment 'videoout'(1 = LCD and 2 = CRT). If videoout is undefined, CRT isassumed.For the CT69000 and SMI_LYNXEM drivers, videomode isselected via environment 'videomode'. Two different waysare possible:- "videomode=num"   'num' is a standard LiLo mode numbers.Following standard modes are supported(* is default):      Colors640x480 800x600 1024x768 1152x864 1280x1024-------------+---------------------------------------------      8 bits |0x301*0x303 0x305  0x161    0x307     15 bits |0x3100x313 0x316  0x162    0x319     16 bits |0x3110x314 0x317  0x163    0x31A     24 bits |0x3120x315 0x318    ?    0x31B-------------+---------------------------------------------(i.e. setenv videomode 317; saveenv; reset;)- "videomode=bootargs" all the video parameters are parsedfrom the bootargs. (See drivers/video/videomodes.c)CONFIG_VIDEO_SED13806Enable Epson SED13806 driver. This driver supports 8bppand 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPPor CONFIG_VIDEO_SED13806_16BPPCONFIG_FSL_DIU_FBEnable the Freescale DIU video driver.Reference boards forSOCs that have a DIU should define this macro to enable DIUsupport, and should also define these other macros:CONFIG_SYS_DIU_ADDRCONFIG_VIDEOCONFIG_CMD_BMPCONFIG_CFB_CONSOLECONFIG_VIDEO_SW_CURSORCONFIG_VGA_AS_SINGLE_DEVICECONFIG_VIDEO_LOGOCONFIG_VIDEO_BMP_LOGOThe DIU driver will look for the 'video-mode' environmentvariable, and if defined, enable the DIU as a console duringboot.  See the documentation file README.video for adescription of this variable.- LCD Support:CONFIG_LCDDefine this to enable LCD support (for output to LCDdisplay); also select one of the supported displaysby defining one of these:CONFIG_ATMEL_LCD:HITACHI TX09D70VM1CCA, 3.5", 240x320.CONFIG_NEC_NL6448AC33:NEC NL6448AC33-18. Active, color, single scan.CONFIG_NEC_NL6448BC20NEC NL6448BC20-08. 6.5", 640x480.Active, color, single scan.CONFIG_NEC_NL6448BC33_54NEC NL6448BC33-54. 10.4", 640x480.Active, color, single scan.CONFIG_SHARP_16x9Sharp 320x240. Active, color, single scan.It isn't 16x9, and I am not sure what it is.CONFIG_SHARP_LQ64D341Sharp LQ64D341 display, 640x480.Active, color, single scan.CONFIG_HLD1045HLD1045 display, 640x480.Active, color, single scan.CONFIG_OPTREX_BWOptrex CBL50840-2 NF-FW 99 22 M5orHitachi LMG6912RPFC-00TorHitachi SP14Q002320x240. Black & white.Normally display is black on white background; defineCONFIG_SYS_WHITE_ON_BLACK to get it inverted.CONFIG_LCD_ALIGNMENTNormally the LCD is page-aligned (typically 4KB). If this isdefined then the LCD will be aligned to this value instead.For ARM it is sometimes useful to use MMU_SECTION_SIZEhere, since it is cheaper to change data cache settings ona per-section basis.CONFIG_CONSOLE_SCROLL_LINESWhen the console need to be scrolled, this is the number oflines to scroll by. It defaults to 1. Increasing this makesthe console jump but can help speed up operation when scrollingis slow.CONFIG_LCD_ROTATIONSometimes, for example if the display is mounted in portraitmode or even if it's mounted landscape but rotated by 180degree,we need to rotate our content of the display relative to theframebuffer, so that user can read the messages which areprinted out.Once CONFIG_LCD_ROTATION is defined, the lcd_console will beinitialized with a given rotation from "vl_rot" out of"vidinfo_t" which is provided by the board specific code.The value for vl_rot is coded as following (matching tofbcon=rotate:<n> linux-kernel commandline):0 = no rotation respectively 0 degree1 = 90 degree rotation2 = 180 degree rotation3 = 270 degree rotationIf CONFIG_LCD_ROTATION is not defined, the console will beinitialized with 0degree rotation.CONFIG_LCD_BMP_RLE8Support drawing of RLE8-compressed bitmaps on the LCD.CONFIG_I2C_EDIDEnables an 'i2c edid' command which can read EDIDinformation over I2C from an attached LCD display.- Splash Screen Support: CONFIG_SPLASH_SCREENIf this option is set, the environment is checked fora variable "splashimage". If found, the usual displayof logo, copyright and system information on the LCDis suppressed and the BMP image at the addressspecified in "splashimage" is loaded instead. Theconsole is redirected to the "nulldev", too. Thisallows for a "silent" boot where a splash screen isloaded very quickly after power-on.CONFIG_SPLASHIMAGE_GUARDIf this option is set, then U-Boot will prevent the environmentvariable "splashimage" from being set to a problematic address(see README.displaying-bmps).This option is useful for targets where, due to alignmentrestrictions, an improperly aligned BMP image will cause a dataabort. If you think you will not have problems with unalignedaccesses (for example because your toolchain prevents them)there is no need to set this option.CONFIG_SPLASH_SCREEN_ALIGNIf this option is set the splash image can be freely positionedon the screen. Environment variable "splashpos" specifies theposition as "x,y". If a positive number is given it is used asnumber of pixel from left/top. If a negative number is given itis used as number of pixel from right/bottom. You can alsospecify 'm' for centering the image.Example:setenv splashpos m,m=> image at center of screensetenv splashpos 30,20=> image at x = 30 and y = 20setenv splashpos -10,m=> vertically centered image   at x = dspWidth - bmpWidth - 9- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIPIf this option is set, additionally to standard BMPimages, gzipped BMP images can be displayed via thesplashscreen support or the bmp command.- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8If this option is set, 8-bit RLE compressed BMP imagescan be displayed via the splashscreen support or thebmp command.- Do compressing for memory range:CONFIG_CMD_ZIPIf this option is set, it would use zlib deflate methodto compress the specified memory at its best effort.- Compression support:CONFIG_GZIPEnabled by default to support gzip compressed images.CONFIG_BZIP2If this option is set, support for bzip2 compressedimages is included. If not, only uncompressed and gzipcompressed images are supported.NOTE: the bzip2 algorithm requires a lot of RAM, sothe malloc area (as defined by CONFIG_SYS_MALLOC_LEN) shouldbe at least 4MB.CONFIG_LZMAIf this option is set, support for lzma compressedimages is included.Note: The LZMA algorithm adds between 2 and 4KB of code and itrequires an amount of dynamic memory that is given by theformula:(1846 + 768 << (lc + lp)) * sizeof(uint16)Where lc and lp stand for, respectively, Literal context bitsand Literal pos bits.This value is upper-bounded by 14MB in the worst case. Anyway,for a ~4MB large kernel image, we have lc=3 and lp=0 for atotal amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that isa very small buffer.Use the lzmainfo tool to determinate the lc and lp values andthen calculate the amount of needed dynamic memory (ensuringthe appropriate CONFIG_SYS_MALLOC_LEN value).CONFIG_LZOIf this option is set, support for LZO compressed imagesis included.- MII/PHY support:CONFIG_PHY_ADDRThe address of PHY on MII bus.CONFIG_PHY_CLOCK_FREQ (ppc4xx)The clock frequency of the MII busCONFIG_PHY_GIGEIf this option is set, support for speed/duplexdetection of gigabit PHY is included.CONFIG_PHY_RESET_DELAYSome PHY like Intel LXT971A need extra delay afterreset before any MII register access is possible.For such PHY, set this option to the usec delayrequired. (minimum 300usec for LXT971A)CONFIG_PHY_CMD_DELAY (ppc4xx)Some PHY like Intel LXT971A need extra delay aftercommand issued before MII status register can be read- IP address:CONFIG_IPADDRDefine a default value for the IP address to use forthe default Ethernet interface, in case this is notdetermined through e.g. bootp.(Environment variable "ipaddr")- Server IP address:CONFIG_SERVERIPDefines a default value for the IP address of a TFTPserver to contact when using the "tftboot" command.(Environment variable "serverip")CONFIG_KEEP_SERVERADDRKeeps the server's MAC address, in the env 'serveraddr'for passing to bootargs (like Linux's netconsole option)- Gateway IP address:CONFIG_GATEWAYIPDefines a default value for the IP address of thedefault router where packets to other networks aresent to.(Environment variable "gatewayip")- Subnet mask:CONFIG_NETMASKDefines a default value for the subnet mask (orrouting prefix) which is used to determine if an IPaddress belongs to the local subnet or needs to beforwarded through a router.(Environment variable "netmask")- Multicast TFTP Mode:CONFIG_MCAST_TFTPDefines whether you want to support multicast TFTP as perrfc-2090; for example to work with atftp.  Lets lots of targetstftp down the same boot image concurrently.  Note: the Ethernetdriver in use must provide a function: mcast() to join/leave amulticast group.- BOOTP Recovery Mode:CONFIG_BOOTP_RANDOM_DELAYIf you have many targets in a network that try toboot using BOOTP, you may want to avoid that allsystems send out BOOTP requests at precisely the samemoment (which would happen for instance at recoveryfrom a power failure, when all systems will try toboot, thus flooding the BOOTP server. DefiningCONFIG_BOOTP_RANDOM_DELAY causes a random delay to beinserted before sending out BOOTP requests. Thefollowing delays are inserted then:1st BOOTP request:delay 0 ... 1 sec2nd BOOTP request:delay 0 ... 2 sec3rd BOOTP request:delay 0 ... 4 sec4th and followingBOOTP requests:delay 0 ... 8 secCONFIG_BOOTP_ID_CACHE_SIZEBOOTP packets are uniquely identified using a 32-bit ID. Theserver will copy the ID from client requests to responses andU-Boot will use this to determine if it is the destination ofan incoming response. Some servers will check that addressesaren't in use before handing them out (usually using an ARPping) and therefore take up to a few hundred milliseconds torespond. Network congestion may also influence the time ittakes for a response to make it back to the client. If thattime is too long, U-Boot will retransmit requests. In orderto allow earlier responses to still be accepted after theseretransmissions, U-Boot's BOOTP client keeps a small cache ofIDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of thiscache. The default is to keep IDs for up to four outstandingrequests. Increasing this will allow U-Boot to accept offersfrom a BOOTP client in networks with unusually high latency.- DHCP Advanced Options:You can fine tune the DHCP functionality by definingCONFIG_BOOTP_* symbols:CONFIG_BOOTP_SUBNETMASKCONFIG_BOOTP_GATEWAYCONFIG_BOOTP_HOSTNAMECONFIG_BOOTP_NISDOMAINCONFIG_BOOTP_BOOTPATHCONFIG_BOOTP_BOOTFILESIZECONFIG_BOOTP_DNSCONFIG_BOOTP_DNS2CONFIG_BOOTP_SEND_HOSTNAMECONFIG_BOOTP_NTPSERVERCONFIG_BOOTP_TIMEOFFSETCONFIG_BOOTP_VENDOREXCONFIG_BOOTP_MAY_FAILCONFIG_BOOTP_SERVERIP - TFTP server will be the serveripenvironment variable, not the BOOTP server.CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not foundafter the configured retry count, the call will failinstead of starting over.  This can be used to fail overto Link-local IP address configuration if the DHCP serveris not available.CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNSserverip from a DHCP server, it is possible that morethan one DNS serverip is offered to the client.If CONFIG_BOOTP_DNS2 is enabled, the secondary DNSserverip will be stored in the additional environmentvariable "dnsip2". The first DNS serverip is alwaysstored in the variable "dnsip", when CONFIG_BOOTP_DNSis defined.CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capableto do a dynamic update of a DNS server. To do this, theyneed the hostname of the DHCP requester.If CONFIG_BOOTP_SEND_HOSTNAME is defined, the contentof the "hostname" environment variable is passed asoption 12 to the DHCP server.CONFIG_BOOTP_DHCP_REQUEST_DELAYA 32bit value in microseconds for a delay betweenreceiving a "DHCP Offer" and sending the "DHCP Request".This fixes a problem with certain DHCP servers that don'trespond 100% of the time to a "DHCP request". E.g. On anAT91RM9200 processor running at 180MHz, this delay neededto be *at least* 15,000 usec before a Windows Server 2003DHCP server would reply 100% of the time. I recommend atleast 50,000 usec to be safe. The alternative is to hopethat one of the retries will be successful but note thatthe DHCP timeout and retry process takes a longer thanthis delay. - Link-local IP address negotiation:Negotiate with other link-local clients on the local networkfor an address that doesn't require explicit configuration.This is especially useful if a DHCP server cannot be guaranteedto exist in all environments that the device must operate.See doc/README.link-local for more information. - CDP Options:CONFIG_CDP_DEVICE_IDThe device id used in CDP trigger frames.CONFIG_CDP_DEVICE_ID_PREFIXA two character string which is prefixed to the MAC addressof the device.CONFIG_CDP_PORT_IDA printf format string which contains the ascii name ofthe port. Normally is set to "eth%d" which setseth0 for the first Ethernet, eth1 for the second etc.CONFIG_CDP_CAPABILITIESA 32bit integer which indicates the device capabilities;0x00000010 for a normal host which does not forwards.CONFIG_CDP_VERSIONAn ascii string containing the version of the software.CONFIG_CDP_PLATFORMAn ascii string containing the name of the platform.CONFIG_CDP_TRIGGERA 32bit integer sent on the trigger.CONFIG_CDP_POWER_CONSUMPTIONA 16bit integer containing the power consumption of thedevice in .1 of milliwatts.CONFIG_CDP_APPLIANCE_VLAN_TYPEA byte containing the id of the VLAN.- Status LED:CONFIG_STATUS_LEDSeveral configurations allow to display the currentstatus using a LED. For instance, the LED will blinkfast while running U-Boot code, stop blinking assoon as a reply to a BOOTP request was received, andstart blinking slow once the Linux kernel is running(supported by a status LED driver in the Linuxkernel). Defining CONFIG_STATUS_LED enables thisfeature in U-Boot.Additional options:CONFIG_GPIO_LEDThe status LED can be connected to a GPIO pin.In such cases, the gpio_led driver can be used as astatus LED backend implementation. Define CONFIG_GPIO_LEDto include the gpio_led driver in the U-Boot binary.CONFIG_GPIO_LED_INVERTED_TABLESome GPIO connected LEDs may have inverted polarity in whichcase the GPIO high value corresponds to LED off state andGPIO low value corresponds to LED on state.In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be definedwith a list of GPIO LEDs that have inverted polarity.- CAN Support:CONFIG_CAN_DRIVERDefining CONFIG_CAN_DRIVER enables CAN driver supporton those systems that support this (optional)feature, like the TQM8xxL modules.- I2C Support:CONFIG_SYS_I2CThis enable the NEW i2c subsystem, and will allow you to usei2c commands at the u-boot command line (as long as you setCONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2cbased realtime clock chips or other i2c devices. Seecommon/cmd_i2c.c for a description of the command lineinterface.ported i2c driver to the new framework:- drivers/i2c/soft_i2c.c:  - activate first bus with CONFIG_SYS_I2C_SOFT define    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE    for defining speed and slave address  - activate second bus with I2C_SOFT_DECLARATIONS2 define    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2    for defining speed and slave address  - activate third bus with I2C_SOFT_DECLARATIONS3 define    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3    for defining speed and slave address  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4    for defining speed and slave address- drivers/i2c/fsl_i2c.c:  - activate i2c driver with CONFIG_SYS_I2C_FSL    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first    bus.  - If your board supports a second fsl i2c bus, define    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset    CONFIG_SYS_FSL_I2C2_SPEED for the speed and    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the    second bus.- drivers/i2c/tegra_i2c.c:  - activate this driver with CONFIG_SYS_I2C_TEGRA  - This driver adds 4 i2c buses with a fix speed from    100000 and the slave addr 0!- drivers/i2c/ppc4xx_i2c.c  - activate this driver with CONFIG_SYS_I2C_PPC4XX  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1- drivers/i2c/i2c_mxc.c  - activate this driver with CONFIG_SYS_I2C_MXC  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVEIf those defines are not set, default value is 100000for speed, and 0 for slave.- drivers/i2c/rcar_i2c.c:  - activate this driver with CONFIG_SYS_I2C_RCAR  - This driver adds 4 i2c buses  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses- drivers/i2c/sh_i2c.c:  - activate this driver with CONFIG_SYS_I2C_SH  - This driver adds from 2 to 5 i2c buses  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4  - CONFIG_SYS_I2C_SH_BASE5 for setting the register channel 5  - CONFIG_SYS_I2C_SH_SPEED5 for for the speed channel 5  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses- drivers/i2c/omap24xx_i2c.c  - activate this driver with CONFIG_SYS_I2C_OMAP24XX  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4- drivers/i2c/zynq_i2c.c  - activate this driver with CONFIG_SYS_I2C_ZYNQ  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr- drivers/i2c/s3c24x0_i2c.c:  - activate this driver with CONFIG_SYS_I2C_S3C24X0  - This driver adds i2c buses (11 for Exynos5250, Exynos5420    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)    with a fix speed from 100000 and the slave addr 0!- drivers/i2c/ihs_i2c.c  - activate this driver with CONFIG_SYS_I2C_IHS  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1additional defines:CONFIG_SYS_NUM_I2C_BUSESHold the number of i2c buses you want to use. If youdon't use/have i2c muxes on your i2c bus, thisis equal to CONFIG_SYS_NUM_I2C_ADAPTERS, and you canomit this define.CONFIG_SYS_I2C_DIRECT_BUSdefine this, if you don't use i2c muxes on your hardware.if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you canomit this define.CONFIG_SYS_I2C_MAX_HOPSdefine how many muxes are maximal consecutively connectedon one i2c bus. If you not use i2c muxes, omit thisdefine.CONFIG_SYS_I2C_BUSEShold a list of buses you want to use, only used ifCONFIG_SYS_I2C_DIRECT_BUS is not defined, for examplea board with CONFIG_SYS_I2C_MAX_HOPS = 1 andCONFIG_SYS_NUM_I2C_BUSES = 9: CONFIG_SYS_I2C_BUSES{{0, {I2C_NULL_HOP}}, \{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \{1, {I2C_NULL_HOP}}, \{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \}which definesbus 0 on adapter 0 without a muxbus 1 on adapter 0 with a PCA9547 on address 0x70 port 1bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5bus 6 on adapter 1 without a muxbus 7 on adapter 1 with a PCA9544 on address 0x72 port 1bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2If you do not have i2c muxes on your board, omit this define.- Legacy I2C Support:CONFIG_HARD_I2CNOTE: It is intended to move drivers to CONFIG_SYS_I2C whichprovides the following compelling advantages:- more than one i2c adapter is usable- approved multibus support- better i2c mux support** Please consider updating your I2C driver now. **These enable legacy I2C serial bus commands. DefiningCONFIG_HARD_I2C will include the appropriate I2C driverfor the selected CPU.This will allow you to use i2c commands at the u-bootcommand line (as long as you set CONFIG_CMD_I2C inCONFIG_COMMANDS) and communicate with i2c based realtimeclock chips. See common/cmd_i2c.c for a description of thecommand line interface.CONFIG_HARD_I2C selects a hardware I2C controller.There are several other quantities that must also bedefined when you define CONFIG_HARD_I2C.In both cases you will need to define CONFIG_SYS_I2C_SPEEDto be the frequency (in Hz) at which you wish your i2c busto run and CONFIG_SYS_I2C_SLAVE to be the address of this node (iethe CPU's i2c node address).Now, the u-boot i2c code for the mpc8xx(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master nodeand so its address should therefore be cleared to 0 (See,eg, MPC823e User's Manual p.16-473). So, setCONFIG_SYS_I2C_SLAVE to 0.CONFIG_SYS_I2C_INIT_MPC5XXXWhen a board is reset during an i2c bus transferchips might think that the current transfer is stillin progress.  Reset the slave devices by sending startcommands until the slave device responds.That's all that's required for CONFIG_HARD_I2C.If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)then the following macros need to be defined (examples arefrom include/configs/lwmon.h):I2C_INIT(Optional). Any commands necessary to enable the I2Ccontroller or configure ports.eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=PB_SCL)I2C_PORT(Only for MPC8260 CPU). The I/O port to use (the codeassumes both bits are on the same port). Valid valuesare 0..3 for ports A..D.I2C_ACTIVEThe code necessary to make the I2C data line active(driven).  If the data line is open collector, thisdefine can be null.eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)I2C_TRISTATEThe code necessary to make the I2C data line tri-stated(inactive).  If the data line is open collector, thisdefine can be null.eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)I2C_READCode that returns true if the I2C data line is high,false if it is low.eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)I2C_SDA(bit)If <bit> is true, sets the I2C data line high. If itis false, it clears it (low).eg: #define I2C_SDA(bit) \if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \elseimmr->im_cpm.cp_pbdat &= ~PB_SDAI2C_SCL(bit)If <bit> is true, sets the I2C clock line high. If itis false, it clears it (low).eg: #define I2C_SCL(bit) \if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \elseimmr->im_cpm.cp_pbdat &= ~PB_SCLI2C_DELAYThis delay is invoked four times per clock cycle so thiscontrols the rate of data transfer.  The data rate thusis 1 / (I2C_DELAY * 4). Often defined to be somethinglike:#define I2C_DELAY  udelay(2)CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDAIf your arch supports the generic GPIO framework (asm/gpio.h),then you may alternatively define the two GPIOs that are to beused as SCL / SDA.  Any of the previous I2C_xxx macros willhave GPIO-based defaults assigned to them as appropriate.You should define these to the GPIO value as given directly tothe generic GPIO functions.CONFIG_SYS_I2C_INIT_BOARDWhen a board is reset during an i2c bus transferchips might think that the current transfer is stillin progress. On some boards it is possible to accessthe i2c SCLK line directly, either by using theprocessor pin as a GPIO or by having a second pinconnected to the bus. If this option is defined acustom i2c_init_board() routine in boards/xxx/board.cis run early in the boot sequence.CONFIG_SYS_I2C_BOARD_LATE_INITAn alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option isdefined a custom i2c_board_late_init() routine inboards/xxx/board.c is run AFTER the operations in i2c_init()is completed. This callpoint can be used to unreset i2c bususing CPU i2c controller register accesses for CPUs whose i2ccontroller provide such a method. It is called at the end ofi2c_init() to allow i2c_init operations to setup the i2c buscontroller on the CPU (e.g. setting bus speed & slave address).CONFIG_I2CFAST (PPC405GP|PPC405EP only)This option enables configuration of bi_iic_fast[] flagsin u-boot bd_info structure based on u-boot environmentvariable "i2cfast". (see also i2cfast)CONFIG_I2C_MULTI_BUSThis option allows the use of multiple I2C buses, each of whichmust have a controller. At any point in time, only one bus isactive. To switch to a different bus, use the 'i2c dev' command.Note that bus numbering is zero-based.CONFIG_SYS_I2C_NOPROBESThis option specifies a list of I2C devices that will be skippedwhen the 'i2c probe' command is issued. If CONFIG_I2C_MULTI_BUSis set, specify a list of bus-device pairs.  Otherwise, specifya 1D array of device addressese.g.#undefCONFIG_I2C_MULTI_BUS#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}will skip addresses 0x50 and 0x68 on a board with one I2C bus#define CONFIG_I2C_MULTI_BUS#define CONFIG_SYS_I2C_MULTI_NOPROBES{{0,0x50},{0,0x68},{1,0x54}}will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1CONFIG_SYS_SPD_BUS_NUMIf defined, then this indicates the I2C bus number for DDR SPD.If not defined, then U-Boot assumes that SPD is on I2C bus 0.CONFIG_SYS_RTC_BUS_NUMIf defined, then this indicates the I2C bus number for the RTC.If not defined, then U-Boot assumes that RTC is on I2C bus 0.CONFIG_SYS_DTT_BUS_NUMIf defined, then this indicates the I2C bus number for the DTT.If not defined, then U-Boot assumes that DTT is on I2C bus 0.CONFIG_SYS_I2C_DTT_ADDR:If defined, specifies the I2C address of the DTT device.If not defined, then U-Boot uses predefined value forspecified DTT device.CONFIG_SOFT_I2C_READ_REPEATED_STARTdefining this will force the i2c_read() function inthe soft_i2c driver to perform an I2C repeated startbetween writing the address pointer and reading thedata.  If this define is omitted the default behaviourof doing a stop-start sequence will be used.  Most I2Cdevices can use either method, but some require one orthe other.- SPI Support:CONFIG_SPIEnables SPI driver (so far only tested withSPI EEPROM, also an instance works with Crystal A/D andD/As on the SACSng board)CONFIG_SH_SPIEnables the driver for SPI controller on SuperH. Currentlyonly SH7757 is supported.CONFIG_SOFT_SPIEnables a software (bit-bang) SPI driver rather thanusing hardware support. This is a general purposedriver that only requires three general I/O port pins(two outputs, one input) to function. If this isdefined, the board configuration must define severalSPI configuration items (port pins to use, etc). Foran example, see include/configs/sacsng.h.CONFIG_HARD_SPIEnables a hardware SPI driver for general-purpose readsand writes.  As with CONFIG_SOFT_SPI, the board configurationmust define a list of chip-select function pointers.Currently supported on some MPC8xxx processors. For anexample, see include/configs/mpc8349emds.h.CONFIG_MXC_SPIEnables the driver for the SPI controllers on i.MX and MXCSoCs. Currently i.MX31/35/51 are supported.CONFIG_SYS_SPI_MXC_WAITTimeout for waiting until spi transfer completed.default: (CONFIG_SYS_HZ/100)     /* 10 ms */- FPGA Support: CONFIG_FPGAEnables FPGA subsystem.CONFIG_FPGA_<vendor>Enables support for specific chip vendors.(ALTERA, XILINX)CONFIG_FPGA_<family>Enables support for FPGA family.(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)CONFIG_FPGA_COUNTSpecify the number of FPGA devices to support.CONFIG_CMD_FPGA_LOADMKEnable support for fpga loadmk commandCONFIG_CMD_FPGA_LOADPEnable support for fpga loadp command - load partial bitstreamCONFIG_CMD_FPGA_LOADBPEnable support for fpga loadbp command - load partial bitstream(Xilinx only)CONFIG_SYS_FPGA_PROG_FEEDBACKEnable printing of hash marks during FPGA configuration.CONFIG_SYS_FPGA_CHECK_BUSYEnable checks on FPGA configuration interface busystatus by the configuration function. This optionwill require a board or device specific function tobe written.CONFIG_FPGA_DELAYIf defined, a function that provides delays in the FPGAconfiguration driver.CONFIG_SYS_FPGA_CHECK_CTRLCAllow Control-C to interrupt FPGA configurationCONFIG_SYS_FPGA_CHECK_ERRORCheck for configuration errors during FPGA bitfileloading. For example, abort during Virtex IIconfiguration if the INIT_B line goes low (whichindicated a CRC error).CONFIG_SYS_FPGA_WAIT_INITMaximum time to wait for the INIT_B line to de-assertafter PROB_B has been de-asserted during a Virtex IIFPGA configuration sequence. The default time is 500ms.CONFIG_SYS_FPGA_WAIT_BUSYMaximum time to wait for BUSY to de-assert duringVirtex II FPGA configuration. The default is 5 ms.CONFIG_SYS_FPGA_WAIT_CONFIGTime to wait after FPGA configuration. The default is200 ms.- Configuration Management:CONFIG_BUILD_TARGETSome SoCs need special image types (e.g. U-Boot binarywith a special header) as build targets. By definingCONFIG_BUILD_TARGET in the SoC / board header, thisspecial image will be automatically built upon callingmake / MAKEALL.CONFIG_IDENT_STRINGIf defined, this string will be added to the U-Bootversion information (U_BOOT_VERSION)- Vendor Parameter Protection:U-Boot considers the values of the environmentvariables "serial#" (Board Serial Number) and"ethaddr" (Ethernet Address) to be parameters thatare set once by the board vendor / manufacturer, andprotects these variables from casual modification bythe user. Once set, these variables are read-only,and write or delete attempts are rejected. You canchange this behaviour:If CONFIG_ENV_OVERWRITE is #defined in your configfile, the write protection for vendor parameters iscompletely disabled. Anybody can change or deletethese parameters.Alternatively, if you define _both_ an ethaddr in thedefault env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a defaultEthernet address is installed in the environment,which can be changed exactly ONCE by the user. [Theserial# is unaffected by this, i. e. it remainsread-only.]The same can be accomplished in a more flexible wayfor any variable by configuring the type of accessto allow for those variables in the ".flags" variableor define CONFIG_ENV_FLAGS_LIST_STATIC.- Protected RAM:CONFIG_PRAMDefine this variable to enable the reservation of"protected RAM", i. e. RAM which is not overwrittenby U-Boot. Define CONFIG_PRAM to hold the number ofkB you want to reserve for pRAM. You can overwritethis default value by defining an environmentvariable "pram" to the number of kB you want toreserve. Note that the board info structure willstill show the full amount of RAM. If pRAM isreserved, a new environment variable "mem" willautomatically be defined to hold the amount ofremaining RAM in a form that can be passed as bootargument to Linux, for instance like that:setenv bootargs ... mem=\${mem}saveenvThis way you can tell Linux not to use this memory,either, which results in a memory region that willnot be affected by reboots.*WARNING* If your board configuration uses automaticdetection of the RAM size, you must make sure thatthis memory test is non-destructive. So far, thefollowing board configurations are known to be"pRAM-clean":IVMS8, IVML24, SPD8xx, TQM8xxL,HERMES, IP860, RPXlite, LWMON,FLAGADM, TQM8260- Access to physical memory region (> 4GB)Some basic support is provided for operations on memory notnormally accessible to U-Boot - e.g. some architecturessupport access to more than 4GB of memory on 32-bitmachines using physical address extension or similar.Define CONFIG_PHYSMEM to access this basic support, whichcurrently only supports clearing the memory.- Error Recovery:CONFIG_PANIC_HANGDefine this variable to stop the system in case of afatal error, so that you have to reset it manually.This is probably NOT a good idea for an embeddedsystem where you want the system to rebootautomatically as fast as possible, but it may beuseful during development since you can try to debugthe conditions that lead to the situation.CONFIG_NET_RETRY_COUNTThis variable defines the number of retries fornetwork operations like ARP, RARP, TFTP, or BOOTPbefore giving up the operation. If not defined, adefault value of 5 is used.CONFIG_ARP_TIMEOUTTimeout waiting for an ARP reply in milliseconds.CONFIG_NFS_TIMEOUTTimeout in milliseconds used in NFS protocol.If you encounter "ERROR: Cannot umount" in nfs command,try longer timeout such as#define CONFIG_NFS_TIMEOUT 10000UL- Command Interpreter:CONFIG_AUTO_COMPLETEEnable auto completion of commands using TAB.CONFIG_SYS_PROMPT_HUSH_PS2This defines the secondary prompt string, which isprinted when the command interpreter needs more inputto complete a command. Usually "> ".Note:In the current implementation, the local variablesspace and global environment variables space areseparated. Local variables are those you define bysimply typing `name=value'. To access a localvariable later on, you have write `$name' or`${name}'; to execute the contents of a variabledirectly type `$name' at the command prompt.Global environment variables are those you usesetenv/printenv to work with. To run a command storedin such a variable, you need to use the run command,and you must not use the '$' sign to access them.To store commands and special characters in avariable, please use double quotation markssurrounding the whole text of the variable, insteadof the backslashes before semicolons and specialsymbols.- Command Line Editing and History:CONFIG_CMDLINE_EDITINGEnable editing and History functions for interactivecommand line input operations- Default Environment:CONFIG_EXTRA_ENV_SETTINGSDefine this to contain any number of null terminatedstrings (variable = value pairs) that will be part ofthe default environment compiled into the boot image.For example, place something like this in yourboard's config file:#define CONFIG_EXTRA_ENV_SETTINGS \"myvar1=value1\0" \"myvar2=value2\0"Warning: This method is based on knowledge about theinternal format how the environment is stored by theU-Boot code. This is NOT an official, exportedinterface! Although it is unlikely that this formatwill change soon, there is no guarantee either.You better know what you are doing here.Note: overly (ab)use of the default environment isdiscouraged. Make sure to check other ways to presetthe environment like the "source" command or theboot command first.CONFIG_ENV_VARS_UBOOT_CONFIGDefine this in order to add variables describing theU-Boot build configuration to the default environment.These will be named arch, cpu, board, vendor, and soc.Enabling this option will cause the following to be defined:- CONFIG_SYS_ARCH- CONFIG_SYS_CPU- CONFIG_SYS_BOARD- CONFIG_SYS_VENDOR- CONFIG_SYS_SOCCONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIGDefine this in order to add variables describing certainrun-time determined information about the hardware to theenvironment.  These will be named board_name, board_rev.CONFIG_DELAY_ENVIRONMENTNormally the environment is loaded when the board isinitialised so that it is available to U-Boot. This inhibitsthat so that the environment is not available untilexplicitly loaded later by U-Boot code. With CONFIG_OF_CONTROLthis is instead controlled by the value of/config/load-environment.- Parallel Flash support:CONFIG_SYS_NO_FLASHTraditionally U-boot was run on systems with parallel NORflash. This option is used to disable support for parallel NORflash. This option should be defined if the board does not haveparallel flash.If this option is not defined one of the generic flash drivers(e.g.  CONFIG_FLASH_CFI_DRIVER or CONFIG_ST_SMI) must beselected or the board must provide an implementation of theflash API (see include/flash.h).- DataFlash Support:CONFIG_HAS_DATAFLASHDefining this option enables DataFlash features andallows to read/write in Dataflash via the standardcommands cp, md...- Serial Flash supportCONFIG_CMD_SFDefining this option enables SPI flash commands'sf probe/read/write/erase/update'.Usage requires an initial 'probe' to define the serialflash parameters, followed by read/write/erase/updatecommands.The following defaults may be provided by the platformto handle the common case when only a single serialflash is present on the system.CONFIG_SF_DEFAULT_BUSBus identifierCONFIG_SF_DEFAULT_CSChip-selectCONFIG_SF_DEFAULT_MODE (see include/spi.h)CONFIG_SF_DEFAULT_SPEEDin HzCONFIG_CMD_SF_TESTDefine this option to include a destructive SPI flashtest ('sf test').CONFIG_SF_DUAL_FLASHDual flash memoriesDefine this option to use dual flash support where two flashmemories can be connected with a given cs line.Currently Xilinx Zynq qspi supports these type of connections.- SystemACE Support:CONFIG_SYSTEMACEAdding this option adds support for Xilinx SystemACEchips attached via some sort of local bus. The addressof the chip must also be defined in theCONFIG_SYS_SYSTEMACE_BASE macro. For example:#define CONFIG_SYSTEMACE#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000When SystemACE support is added, the "ace" device typebecomes available to the fat commands, i.e. fatls.- TFTP Fixed UDP Port:CONFIG_TFTP_PORTIf this is defined, the environment variable tftpsrcpis used to supply the TFTP UDP source port value.If tftpsrcp isn't defined, the normal pseudo-random portnumber generator is used.Also, the environment variable tftpdstp is used to supplythe TFTP UDP destination port value.  If tftpdstp isn'tdefined, the normal port 69 is used.The purpose for tftpsrcp is to allow a TFTP server toblindly start the TFTP transfer using the pre-configuredtarget IP address and UDP port. This has the effect of"punching through" the (Windows XP) firewall, allowingthe remainder of the TFTP transfer to proceed normally.A better solution is to properly configure the firewall,but sometimes that is not allowed.- Hashing support:CONFIG_CMD_HASHThis enables a generic 'hash' command which can producehashes / digests from a few algorithms (e.g. SHA1, SHA256).CONFIG_HASH_VERIFYEnable the hash verify command (hash -v). This adds to codesize a little.CONFIG_SHA1 - This option enables support of hashing using SHA1algorithm. The hash is calculated in software.CONFIG_SHA256 - This option enables support of hashing usingSHA256 algorithm. The hash is calculated in software.CONFIG_SHA_HW_ACCEL - This option enables hardware accelerationfor SHA1/SHA256 hashing.This affects the 'hash' command and also thehash_lookup_algo() function.CONFIG_SHA_PROG_HW_ACCEL - This option enableshardware-acceleration for SHA1/SHA256 progressive hashing.Data can be streamed in a block at a time and the hashingis performed in hardware.Note: There is also a sha1sum command, which should perhapsbe deprecated in favour of 'hash sha1'.- Freescale i.MX specific commands:CONFIG_CMD_HDMIDETECTThis enables 'hdmidet' command which returns true if anHDMI monitor is detected.  This command is i.MX 6 specific.CONFIG_CMD_BMODEThis enables the 'bmode' (bootmode) command for forcinga boot from specific media.This is useful for forcing the ROM's usb downloader toactivate upon a watchdog reset which is nice when iteratingon U-Boot.  Using the reset button or running bmode normalwill set it back to normal.  This command currentlysupports i.MX53 and i.MX6.- Signing support:CONFIG_RSAThis enables the RSA algorithm used for FIT image verificationin U-Boot. See doc/uImage.FIT/signature.txt for more information.The Modular Exponentiation algorithm in RSA is implemented usingdriver model. So CONFIG_DM needs to be enabled by default for thislibrary to function.The signing part is build into mkimage regardless of thisoption. The software based modular exponentiation is built intomkimage irrespective of this option.- bootcount support:CONFIG_BOOTCOUNT_LIMITThis enables the bootcounter support, see:http://www.denx.de/wiki/DULG/UBootBootCountLimitCONFIG_AT91SAM9XEenable special bootcounter support on at91sam9xe based boards.CONFIG_BLACKFINenable special bootcounter support on blackfin based boards.CONFIG_SOC_DA8XXenable special bootcounter support on da850 based boards.CONFIG_BOOTCOUNT_RAMenable support for the bootcounter in RAMCONFIG_BOOTCOUNT_I2Cenable support for the bootcounter on an i2c (like RTC) device.CONFIG_SYS_I2C_RTC_ADDR = i2c chip addressCONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for    the bootcounter.CONFIG_BOOTCOUNT_ALEN = address len- Show boot progress:CONFIG_SHOW_BOOT_PROGRESSDefining this option allows to add some board-specific code (calling a user-provided function"show_boot_progress(int)") that enables you to showthe system's boot progress on some display (forexample, some LED's) on your board. At the moment,the following checkpoints are implemented:Legacy uImage format:  ArgWhereWhen    1common/cmd_bootm.cbefore attempting to boot an image   -1common/cmd_bootm.cImage header has bad magic number    2common/cmd_bootm.cImage header has correct magic number   -2common/cmd_bootm.cImage header has bad checksum    3common/cmd_bootm.cImage header has correct checksum   -3common/cmd_bootm.cImage data   has bad checksum    4common/cmd_bootm.cImage data   has correct checksum   -4common/cmd_bootm.cImage is for unsupported architecture    5common/cmd_bootm.cArchitecture check OK   -5common/cmd_bootm.cWrong Image Type (not kernel, multi)    6common/cmd_bootm.cImage Type check OK   -6common/cmd_bootm.cgunzip uncompression error   -7common/cmd_bootm.cUnimplemented compression type    7common/cmd_bootm.cUncompression OK    8common/cmd_bootm.cNo uncompress/copy overwrite error   -9common/cmd_bootm.cUnsupported OS (not Linux, BSD, VxWorks, QNX)    9common/image.cStart initial ramdisk verification  -10common/image.cRamdisk header has bad   magic number  -11common/image.cRamdisk header has bad   checksum   10common/image.cRamdisk header is OK  -12common/image.cRamdisk data   has bad   checksum   11common/image.cRamdisk data   has correct checksum   12common/image.cRamdisk verification complete, start loading  -13common/image.cWrong Image Type (not PPC Linux ramdisk)   13common/image.cStart multifile image verification   14common/image.cNo initial ramdisk, no multifile, continue.   15arch/<arch>/lib/bootm.c All preparation done, transferring control to OS  -30arch/powerpc/lib/board.cFatal error, hang the system  -31post/post.cPOST test failed, detected by post_output_backlog()  -32post/post.cPOST test failed, detected by post_run_single()   34common/cmd_doc.cbefore loading a Image from a DOC device  -35common/cmd_doc.cBad usage of "doc" command   35common/cmd_doc.ccorrect usage of "doc" command  -36common/cmd_doc.cNo boot device   36common/cmd_doc.ccorrect boot device  -37common/cmd_doc.cUnknown Chip ID on boot device   37common/cmd_doc.ccorrect chip ID found, device available  -38common/cmd_doc.cRead Error on boot device   38common/cmd_doc.creading Image header from DOC device OK  -39common/cmd_doc.cImage header has bad magic number   39common/cmd_doc.cImage header has correct magic number  -40common/cmd_doc.cError reading Image from DOC device   40common/cmd_doc.cImage header has correct magic number   41common/cmd_ide.cbefore loading a Image from a IDE device  -42common/cmd_ide.cBad usage of "ide" command   42common/cmd_ide.ccorrect usage of "ide" command  -43common/cmd_ide.cNo boot device   43common/cmd_ide.cboot device found  -44common/cmd_ide.cDevice not available   44common/cmd_ide.cDevice available  -45common/cmd_ide.cwrong partition selected   45common/cmd_ide.cpartition selected  -46common/cmd_ide.cUnknown partition table   46common/cmd_ide.cvalid partition table found  -47common/cmd_ide.cInvalid partition type   47common/cmd_ide.ccorrect partition type  -48common/cmd_ide.cError reading Image Header on boot device   48common/cmd_ide.creading Image Header from IDE device OK  -49common/cmd_ide.cImage header has bad magic number   49common/cmd_ide.cImage header has correct magic number  -50common/cmd_ide.cImage header has bad checksum   50common/cmd_ide.cImage header has correct checksum  -51common/cmd_ide.cError reading Image from IDE device   51common/cmd_ide.creading Image from IDE device OK   52common/cmd_nand.cbefore loading a Image from a NAND device  -53common/cmd_nand.cBad usage of "nand" command   53common/cmd_nand.ccorrect usage of "nand" command  -54common/cmd_nand.cNo boot device   54common/cmd_nand.cboot device found  -55common/cmd_nand.cUnknown Chip ID on boot device   55common/cmd_nand.ccorrect chip ID found, device available  -56common/cmd_nand.cError reading Image Header on boot device   56common/cmd_nand.creading Image Header from NAND device OK  -57common/cmd_nand.cImage header has bad magic number   57common/cmd_nand.cImage header has correct magic number  -58common/cmd_nand.cError reading Image from NAND device   58common/cmd_nand.creading Image from NAND device OK  -60common/env_common.cEnvironment has a bad CRC, using default   64net/eth.cstarting with Ethernet configuration.  -64net/eth.cno Ethernet found.   65net/eth.cEthernet found.  -80common/cmd_net.cusage wrong   80common/cmd_net.cbefore calling net_loop()  -81common/cmd_net.csome error in net_loop() occurred   81common/cmd_net.cnet_loop() back without error  -82common/cmd_net.csize == 0 (File with size 0 loaded)   82common/cmd_net.ctrying automatic boot   83common/cmd_net.crunning "source" command  -83common/cmd_net.csome error in automatic boot or "source" command   84common/cmd_net.cend without errorsFIT uImage format:  ArgWhereWhen  100common/cmd_bootm.cKernel FIT Image has correct format -100common/cmd_bootm.cKernel FIT Image has incorrect format  101common/cmd_bootm.cNo Kernel subimage unit name, using configuration -101common/cmd_bootm.cCan't get configuration for kernel subimage  102common/cmd_bootm.cKernel unit name specified -103common/cmd_bootm.cCan't get kernel subimage node offset  103common/cmd_bootm.cFound configuration node  104common/cmd_bootm.cGot kernel subimage node offset -104common/cmd_bootm.cKernel subimage hash verification failed  105common/cmd_bootm.cKernel subimage hash verification OK -105common/cmd_bootm.cKernel subimage is for unsupported architecture  106common/cmd_bootm.cArchitecture check OK -106common/cmd_bootm.cKernel subimage has wrong type  107common/cmd_bootm.cKernel subimage type OK -107common/cmd_bootm.cCan't get kernel subimage data/size  108common/cmd_bootm.cGot kernel subimage data/size -108common/cmd_bootm.cWrong image type (not legacy, FIT) -109common/cmd_bootm.cCan't get kernel subimage type -110common/cmd_bootm.cCan't get kernel subimage comp -111common/cmd_bootm.cCan't get kernel subimage os -112common/cmd_bootm.cCan't get kernel subimage load address -113common/cmd_bootm.cImage uncompress/copy overwrite error  120common/image.cStart initial ramdisk verification -120common/image.cRamdisk FIT image has incorrect format  121common/image.cRamdisk FIT image has correct format  122common/image.cNo ramdisk subimage unit name, using configuration -122common/image.cCan't get configuration for ramdisk subimage  123common/image.cRamdisk unit name specified -124common/image.cCan't get ramdisk subimage node offset  125common/image.cGot ramdisk subimage node offset -125common/image.cRamdisk subimage hash verification failed  126common/image.cRamdisk subimage hash verification OK -126common/image.cRamdisk subimage for unsupported architecture  127common/image.cArchitecture check OK -127common/image.cCan't get ramdisk subimage data/size  128common/image.cGot ramdisk subimage data/size  129common/image.cCan't get ramdisk load address -129common/image.cGot ramdisk load address -130common/cmd_doc.cIncorrect FIT image format  131common/cmd_doc.cFIT image format OK -140common/cmd_ide.cIncorrect FIT image format  141common/cmd_ide.cFIT image format OK -150common/cmd_nand.cIncorrect FIT image format  151common/cmd_nand.cFIT image format OK- legacy image format:CONFIG_IMAGE_FORMAT_LEGACYenables the legacy image format support in U-Boot.Default:enabled if CONFIG_FIT_SIGNATURE is not defined.CONFIG_DISABLE_IMAGE_LEGACYdisable the legacy image formatThis define is introduced, as the legacy image format isenabled per default for backward compatibility.- FIT image support:CONFIG_FITEnable support for the FIT uImage format.CONFIG_FIT_BEST_MATCHWhen no configuration is explicitly selected, default to theone whose fdt's compatibility field best matches that ofU-Boot itself. A match is considered "best" if it matches themost specific compatibility entry of U-Boot's fdt's root node.The order of entries in the configuration's fdt is ignored.CONFIG_FIT_SIGNATUREThis option enables signature verification of FIT uImages,using a hash signed and verified using RSA. IfCONFIG_SHA_PROG_HW_ACCEL is defined, i.e support for progressivehashing is available using hardware, RSA library will use it.See doc/uImage.FIT/signature.txt for more details.WARNING: When relying on signed FIT images with requiredsignature check the legacy image format is defaultdisabled. If a board need legacy image format supportenable this through CONFIG_IMAGE_FORMAT_LEGACYCONFIG_FIT_DISABLE_SHA256Supporting SHA256 hashes has quite an impact on binary size.For constrained systems sha256 hash support can be disabledwith this option.- Standalone program support:CONFIG_STANDALONE_LOAD_ADDRThis option defines a board specific value for theaddress where standalone program gets loaded, thusoverwriting the architecture dependent defaultsettings.- Frame Buffer Address:CONFIG_FB_ADDRDefine CONFIG_FB_ADDR if you want to use specificaddress for frame buffer.  This is typically the casewhen using a graphics controller has separate videomemory.  U-Boot will then place the frame buffer atthe given address instead of dynamically reserving itin system RAM by calling lcd_setmem(), which grabsthe memory for the frame buffer depending on theconfigured panel size.Please see board_init_f function.- Automatic software updates via TFTP serverCONFIG_UPDATE_TFTPCONFIG_UPDATE_TFTP_CNT_MAXCONFIG_UPDATE_TFTP_MSEC_MAXThese options enable and control the auto-update feature;for a more detailed description refer to doc/README.update.- MTD Support (mtdparts command, UBI support)CONFIG_MTD_DEVICEAdds the MTD device infrastructure from the Linux kernel.Needed for mtdparts command support.CONFIG_MTD_PARTITIONSAdds the MTD partitioning infrastructure from the Linuxkernel. Needed for UBI support.- UBI supportCONFIG_CMD_UBIAdds commands for interacting with MTD partitions formattedwith the UBI flash translation layerRequires also defining CONFIG_RBTREECONFIG_UBI_SILENCE_MSGMake the verbose messages from UBI stop printing.  This leaveswarnings and errors enabled.CONFIG_MTD_UBI_WL_THRESHOLDThis parameter defines the maximum difference between the highesterase counter value and the lowest erase counter value of eraseblocksof UBI devices. When this threshold is exceeded, UBI starts performingwear leveling by means of moving data from eraseblock with low erasecounter to eraseblocks with high erase counter.The default value should be OK for SLC NAND flashes, NOR flashes andother flashes which have eraseblock life-cycle 100000 or more.However, in case of MLC NAND flashes which typically have eraseblocklife-cycle less than 10000, the threshold should be lessened (e.g.,to 128 or 256, although it does not have to be power of 2).default: 4096CONFIG_MTD_UBI_BEB_LIMITThis option specifies the maximum bad physical eraseblocks UBIexpects on the MTD device (per 1024 eraseblocks). If theunderlying flash does not admit of bad eraseblocks (e.g. NORflash), this value is ignored.NAND datasheets often specify the minimum and maximum NVM(Number of Valid Blocks) for the flashes' endurance lifetime.The maximum expected bad eraseblocks per 1024 eraseblocksthen can be calculated as "1024 * (1 - MinNVB / MaxNVB)",which gives 20 for most NANDs (MaxNVB is basically the totalcount of eraseblocks on the chip).To put it differently, if this value is 20, UBI will try toreserve about 1.9% of physical eraseblocks for bad blockshandling. And that will be 1.9% of eraseblocks on the entireNAND chip, not just the MTD partition UBI attaches. This meansthat if you have, say, a NAND flash chip admits maximum 40 baderaseblocks, and it is split on two MTD partitions of the samesize, UBI will reserve 40 eraseblocks when attaching apartition.default: 20CONFIG_MTD_UBI_FASTMAPFastmap is a mechanism which allows attaching an UBI devicein nearly constant time. Instead of scanning the whole MTD device itonly has to locate a checkpoint (called fastmap) on the device.The on-flash fastmap contains all information needed to attachthe device. Using fastmap makes only sense on large devices whereattaching by scanning takes long. UBI will not automatically installa fastmap on old images, but you can set the UBI parameterCONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please notethat fastmap-enabled images are still usable with UBI implementationswithoutfastmap support. On typical flash devices the whole fastmapfits into one PEB. UBI will reserve PEBs to hold two fastmaps.CONFIG_MTD_UBI_FASTMAP_AUTOCONVERTSet this parameter to enable fastmap automatically on imageswithout a fastmap.default: 0CONFIG_MTD_UBI_FM_DEBUGEnable UBI fastmap debugdefault: 0- UBIFS supportCONFIG_CMD_UBIFSAdds commands for interacting with UBI volumes formatted asUBIFS.  UBIFS is read-only in u-boot.Requires UBI support as well as CONFIG_LZOCONFIG_UBIFS_SILENCE_MSGMake the verbose messages from UBIFS stop printing.  This leaveswarnings and errors enabled.- SPL frameworkCONFIG_SPLEnable building of SPL globally.CONFIG_SPL_LDSCRIPTLDSCRIPT for linking the SPL binary.CONFIG_SPL_MAX_FOOTPRINTMaximum size in memory allocated to the SPL, BSS included.When defined, the linker checks that the actual memoryused by SPL from _start to __bss_end does not exceed it.CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZEmust not be both defined at the same time.CONFIG_SPL_MAX_SIZEMaximum size of the SPL image (text, data, rodata, andlinker lists sections), BSS excluded.When defined, the linker checks that the actual size doesnot exceed it.CONFIG_SPL_TEXT_BASETEXT_BASE for linking the SPL binary.CONFIG_SPL_RELOC_TEXT_BASEAddress to relocate to.  If unspecified, this is equal toCONFIG_SPL_TEXT_BASE (i.e. no relocation is done).CONFIG_SPL_BSS_START_ADDRLink address for the BSS within the SPL binary.CONFIG_SPL_BSS_MAX_SIZEMaximum size in memory allocated to the SPL BSS.When defined, the linker checks that the actual memory usedby SPL from __bss_start to __bss_end does not exceed it.CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZEmust not be both defined at the same time.CONFIG_SPL_STACKAdress of the start of the stack SPL will useCONFIG_SPL_PANIC_ON_RAW_IMAGEWhen defined, SPL will panic() if the image it hasloaded does not have a signature.Defining this is useful when code which loads imagesin SPL cannot guarantee that absolutely all read errorswill be caught.An example is the LPC32XX MLC NAND driver, which willconsider that a completely unreadable NAND block is bad,and thus should be skipped silently.CONFIG_SPL_RELOC_STACKAdress of the start of the stack SPL will use afterrelocation.  If unspecified, this is equal toCONFIG_SPL_STACK.CONFIG_SYS_SPL_MALLOC_STARTStarting address of the malloc pool used in SPL.When this option is set the full malloc is used in SPL andit is set up by spl_init() and before that, the simple malloc()can be used if CONFIG_SYS_MALLOC_F is defined.CONFIG_SYS_SPL_MALLOC_SIZEThe size of the malloc pool used in SPL.CONFIG_SPL_FRAMEWORKEnable the SPL framework under common/.  This frameworksupports MMC, NAND and YMODEM loading of U-Boot and NANDNAND loading of the Linux Kernel.CONFIG_SPL_OS_BOOTEnable booting directly to an OS from SPL.See also: doc/README.falconCONFIG_SPL_DISPLAY_PRINTFor ARM, enable an optional function to print more informationabout the running system.CONFIG_SPL_INIT_MINIMALArch init code should be built for a very small imageCONFIG_SPL_LIBCOMMON_SUPPORTSupport for common/libcommon.o in SPL binaryCONFIG_SPL_LIBDISK_SUPPORTSupport for disk/libdisk.o in SPL binaryCONFIG_SPL_I2C_SUPPORTSupport for drivers/i2c/libi2c.o in SPL binaryCONFIG_SPL_GPIO_SUPPORTSupport for drivers/gpio/libgpio.o in SPL binaryCONFIG_SPL_MMC_SUPPORTSupport for drivers/mmc/libmmc.o in SPL binaryCONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,Address and partition on the MMC to load U-Boot fromwhen the MMC is being used in raw mode.CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITIONPartition on the MMC to load U-Boot from when the MMC is beingused in raw modeCONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTORSector to load kernel uImage from when MMC is beingused in raw mode (for Falcon mode)CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORSSector and number of sectors to load kernel argumentparameters from when MMC is being used in raw mode(for falcon mode)CONFIG_SYS_MMCSD_FS_BOOT_PARTITIONPartition on the MMC to load U-Boot from when the MMC is beingused in fs modeCONFIG_SPL_FAT_SUPPORTSupport for fs/fat/libfat.o in SPL binaryCONFIG_SPL_EXT_SUPPORTSupport for EXT filesystem in SPL binaryCONFIG_SPL_FS_LOAD_PAYLOAD_NAMEFilename to read to load U-Boot when reading from filesystemCONFIG_SPL_FS_LOAD_KERNEL_NAMEFilename to read to load kernel uImage when readingfrom filesystem (for Falcon mode)CONFIG_SPL_FS_LOAD_ARGS_NAMEFilename to read to load kernel argument parameterswhen reading from filesystem (for Falcon mode)CONFIG_SPL_MPC83XX_WAIT_FOR_NANDSet this for NAND SPL on PPC mpc83xx targets, so thatstart.S waits for the rest of the SPL to load beforecontinuing (the hardware starts execution after justloading the first page rather than the full 4K).CONFIG_SPL_SKIP_RELOCATEAvoid SPL relocationCONFIG_SPL_NAND_BASEInclude nand_base.c in the SPL.  RequiresCONFIG_SPL_NAND_DRIVERS.CONFIG_SPL_NAND_DRIVERSSPL uses normal NAND drivers, not minimal drivers.CONFIG_SPL_NAND_ECCInclude standard software ECC in the SPLCONFIG_SPL_NAND_SIMPLESupport for NAND boot using simple NAND drivers thatexpose the cmd_ctrl() interface.CONFIG_SPL_MTD_SUPPORTSupport for the MTD subsystem within SPL.  Useful forenvironment on NAND support within SPL.CONFIG_SPL_NAND_RAW_ONLYSupport to boot only raw u-boot.bin images. Use this onlyif you need to save space.CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORTSet for the SPL on PPC mpc8xxx targets, support fordrivers/ddr/fsl/libddr.o in SPL binary.CONFIG_SPL_COMMON_INIT_DDRSet for common ddr init with serial presence detect inSPL binary.CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,CONFIG_SYS_NAND_ECCBYTESDefines the size and behavior of the NAND that SPL usesto read U-BootCONFIG_SPL_NAND_BOOTAdd support NAND bootCONFIG_SYS_NAND_U_BOOT_OFFSLocation in NAND to read U-Boot fromCONFIG_SYS_NAND_U_BOOT_DSTLocation in memory to load U-Boot toCONFIG_SYS_NAND_U_BOOT_SIZESize of image to loadCONFIG_SYS_NAND_U_BOOT_STARTEntry point in loaded image to jump toCONFIG_SYS_NAND_HW_ECC_OOBFIRSTDefine this if you need to first read the OOB and then thedata. This is used, for example, on davinci platforms.CONFIG_SPL_OMAP3_ID_NANDSupport for an OMAP3-specific set of functions to return theID and MFR of the first attached NAND chip, if present.CONFIG_SPL_SERIAL_SUPPORTSupport for drivers/serial/libserial.o in SPL binaryCONFIG_SPL_SPI_FLASH_SUPPORTSupport for drivers/mtd/spi/libspi_flash.o in SPL binaryCONFIG_SPL_SPI_SUPPORTSupport for drivers/spi/libspi.o in SPL binaryCONFIG_SPL_RAM_DEVICESupport for running image already present in ram, in SPL binaryCONFIG_SPL_LIBGENERIC_SUPPORTSupport for lib/libgeneric.o in SPL binaryCONFIG_SPL_ENV_SUPPORTSupport for the environment operating in SPL binaryCONFIG_SPL_NET_SUPPORTSupport for the net/libnet.o in SPL binary.It conflicts with SPL env from storage medium specified byCONFIG_ENV_IS_xxx but CONFIG_ENV_IS_NOWHERECONFIG_SPL_PAD_TOImage offset to which the SPL should be padded before appendingthe SPL payload. By default, this is defined asCONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPLpayload without any padding, or >= CONFIG_SPL_MAX_SIZE.CONFIG_SPL_TARGETFinal target image containing SPL and payload.  Some SPLsuse an arch-specific makefile fragment instead, forexample if more than one image needs to be produced.CONFIG_FIT_SPL_PRINTPrinting information about a FIT image adds quite a bit ofcode to SPL. So this is normally disabled in SPL. Use thisoption to re-enable it. This will affect the output of thebootm command when booting a FIT image.- TPL frameworkCONFIG_TPLEnable building of TPL globally.CONFIG_TPL_PAD_TOImage offset to which the TPL should be padded before appendingthe TPL payload. By default, this is defined asCONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPLpayload without any padding, or >= CONFIG_SPL_MAX_SIZE.Modem Support:--------------[so far only for SMDK2400 boards]- Modem support enable:CONFIG_MODEM_SUPPORT- RTS/CTS Flow control enable:CONFIG_HWFLOW- Modem debug support:CONFIG_MODEM_SUPPORT_DEBUGEnables debugging stuff (char screen[1024], dbg())for modem support. Useful only with BDI2000.- Interrupt support (PPC):There are common interrupt_init() and timer_interrupt()for all PPC archs. interrupt_init() calls interrupt_init_cpu()for CPU specific initialization. interrupt_init_cpu()should set decrementer_count to appropriate value. IfCPU resets decrementer automatically after interrupt(ppc4xx) it should set decrementer_count to zero.timer_interrupt() calls timer_interrupt_cpu() for CPUspecific handling. If board has watchdog / status_led/ other_activity_monitor it works automatically fromgeneral timer_interrupt().- General:In the target system modem support is enabled when aspecific key (key combination) is pressed duringpower-on. Otherwise U-Boot will boot normally(autoboot). The key_pressed() function is called fromboard_init(). Currently key_pressed() is a dummyfunction, returning 1 and thus enabling modeminitialization.If there are no modem init strings in theenvironment, U-Boot proceed to autoboot; theprevious output (banner, info printfs) will besuppressed, though.See also: doc/README.ModemBoard initialization settings:------------------------------During Initialization u-boot calls a number of board specific functionsto allow the preparation of board specific prerequisites, e.g. pin setupbefore drivers are initialized. To enable these callbacks thefollowing configuration macros have to be defined. Currently this isarchitecture specific, so please check arch/your_architecture/lib/board.ctypically in board_init_f() and board_init_r().- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()- CONFIG_BOARD_LATE_INIT: Call board_late_init()- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()Configuration Settings:------------------------ CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.Optionally it can be defined to support 64-bit memory commands.- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;undefine this when you're short of memory.- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the defaultwidth of the commands listed in the 'help' command output.- CONFIG_SYS_PROMPT:This is what U-Boot prints on the console toprompt for user input.- CONFIG_SYS_CBSIZE:Buffer size for input from the Console- CONFIG_SYS_PBSIZE:Buffer size for Console output- CONFIG_SYS_MAXARGS:max. Number of arguments accepted for monitor commands- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed tothe application (usually a Linux kernel) when it isbooted- CONFIG_SYS_BAUDRATE_TABLE:List of legal baudrate settings for this board.- CONFIG_SYS_CONSOLE_INFO_QUIETSuppress display of console information at boot.- CONFIG_SYS_CONSOLE_IS_IN_ENVIf the board specific functionextern int overwrite_console (void);returns 1, the stdin, stderr and stdout are switched to theserial port, else the settings in the environment are used.- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINEEnable the call to overwrite_console().- CONFIG_SYS_CONSOLE_ENV_OVERWRITEEnable overwrite of previous console environment settings.- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:Begin and End addresses of the area used by thesimple memory test.- CONFIG_SYS_ALT_MEMTEST:Enable an alternate, more extensive memory test.- CONFIG_SYS_MEMTEST_SCRATCH:Scratch address used by the alternate memory testYou only need to set this if address zero isn't writeable- CONFIG_SYS_MEM_TOP_HIDE (PPC only):If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,this specified memory area will get subtracted from the top(end) of RAM and won't get "touched" at all by U-Boot. Byfixing up gd->ram_size the Linux kernel should gets passedthe now "corrected" memory size and won't touch it either.This should work for arch/ppc and arch/powerpc. Only Linuxboard ports in arch/powerpc with bootwrapper support thatrecalculate the memory size from the SDRAM controller setupwill have to get fixed in Linux additionally.This option can be used as a workaround for the 440EPx/GRxCHIP 11 errata where the last 256 bytes in SDRAM shouldn'tbe touched.WARNING: Please make sure that this value is a multiple ofthe Linux page size (normally 4k). If this is not the case,then the end address of the Linux memory will be located at anon page size aligned address and this could cause majorproblems.- CONFIG_SYS_LOADS_BAUD_CHANGE:Enable temporary baudrate change while serial download- CONFIG_SYS_SDRAM_BASE:Physical start address of SDRAM. _Must_ be 0 here.- CONFIG_SYS_MBIO_BASE:Physical start address of Motherboard I/O (if using aCogent motherboard)- CONFIG_SYS_FLASH_BASE:Physical start address of Flash memory.- CONFIG_SYS_MONITOR_BASE:Physical start address of boot monitor code (set bymake config files to be same as the text base address(CONFIG_SYS_TEXT_BASE) used when linking) - same asCONFIG_SYS_FLASH_BASE when booting from flash.- CONFIG_SYS_MONITOR_LEN:Size of memory reserved for monitor code, used todetermine _at_compile_time_ (!) if the environment isembedded within the U-Boot image, or in a separateflash sector.- CONFIG_SYS_MALLOC_LEN:Size of DRAM reserved for malloc() use.- CONFIG_SYS_MALLOC_F_LENSize of the malloc() pool for use before relocation. Ifthis is defined, then a very simple malloc() implementationwill become available before relocation. The address is justbelow the global data, and the stack is moved down to makespace.This feature allocates regions with increasing addresseswithin the region. calloc() is supported, but realloc()is not available. free() is supported but does nothing.The memory will be freed (or in fact just forgotten) whenU-Boot relocates itself.Pre-relocation malloc() is only supported on ARM and sandboxat present but is fairly easy to enable for other archs.- CONFIG_SYS_MALLOC_SIMPLEProvides a simple and small malloc() and calloc() for thoseboards which do not use the full malloc in SPL (which isenabled with CONFIG_SYS_SPL_MALLOC_START).- CONFIG_SYS_NONCACHED_MEMORY:Size of non-cached memory area. This area of memory will betypically located right below the malloc() area and mappeduncached in the MMU. This is useful for drivers that wouldotherwise require a lot of explicit cache maintenance. Forsome drivers it's also impossible to properly maintain thecache. For example if the regions that need to be flushedare not a multiple of the cache-line size, *and* paddingcannot be allocated between the regions to align them (i.e.if the HW requires a contiguous array of regions, and thesize of each region is not cache-aligned), then a flush ofone region may result in overwriting data that hardware haswritten to another region in the same cache-line. This canhappen for example in network drivers where descriptors forbuffers are typically smaller than the CPU cache-line (e.g.16 bytes vs. 32 or 64 bytes).Non-cached memory is only supported on 32-bit ARM at present.- CONFIG_SYS_BOOTM_LEN:Normally compressed uImages are limited to anuncompressed size of 8 MBytes. If this is not enough,you can define CONFIG_SYS_BOOTM_LEN in your board config fileto adjust this setting to your needs.- CONFIG_SYS_BOOTMAPSZ:Maximum size of memory mapped by the startup code ofthe Linux kernel; all data that must be processed bythe Linux kernel (bd_info, boot arguments, FDT blob ifused) must be put below this limit, unless "bootm_low"environment variable is defined and non-zero. In such caseall data for the Linux kernel must be between "bootm_low"and "bootm_low" + CONFIG_SYS_BOOTMAPSZ. The environmentvariable "bootm_mapsize" will override the value ofCONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,then the value in "bootm_size" will be used instead.- CONFIG_SYS_BOOT_RAMDISK_HIGH:Enable initrd_high functionality.  If defined then theinitrd_high feature is enabled and the bootm ramdisk subcommandis enabled.- CONFIG_SYS_BOOT_GET_CMDLINE:Enables allocating and saving kernel cmdline in space between"bootm_low" and "bootm_low" + BOOTMAPSZ.- CONFIG_SYS_BOOT_GET_KBD:Enables allocating and saving a kernel copy of the bd_info inspace between "bootm_low" and "bootm_low" + BOOTMAPSZ.- CONFIG_SYS_MAX_FLASH_BANKS:Max number of Flash memory banks- CONFIG_SYS_MAX_FLASH_SECT:Max number of sectors on a Flash chip- CONFIG_SYS_FLASH_ERASE_TOUT:Timeout for Flash erase operations (in ms)- CONFIG_SYS_FLASH_WRITE_TOUT:Timeout for Flash write operations (in ms)- CONFIG_SYS_FLASH_LOCK_TOUTTimeout for Flash set sector lock bit operation (in ms)- CONFIG_SYS_FLASH_UNLOCK_TOUTTimeout for Flash clear lock bits operation (in ms)- CONFIG_SYS_FLASH_PROTECTIONIf defined, hardware flash sectors protection is usedinstead of U-Boot software protection.- CONFIG_SYS_DIRECT_FLASH_TFTP:Enable TFTP transfers directly to flash memory;without this option such a download has to beperformed in two steps: (1) download to RAM, and (2)copy from RAM to flash.The two-step approach is usually more reliable, sinceyou can check if the download worked before you erasethe flash, but in some situations (when system RAM istoo limited to allow for a temporary copy of thedownloaded image) this option may be very useful.- CONFIG_SYS_FLASH_CFI:Define if the flash driver uses extra elements in thecommon flash structure for storing flash geometry.- CONFIG_FLASH_CFI_DRIVERThis option also enables the building of the cfi_flash driverin the drivers directory- CONFIG_FLASH_CFI_MTDThis option enables the building of the cfi_mtd driverin the drivers directory. The driver exports CFI flashto the MTD layer.- CONFIG_SYS_FLASH_USE_BUFFER_WRITEUse buffered writes to flash.- CONFIG_FLASH_SPANSION_S29WS_Ns29ws-n MirrorBit flash has non-standard addresses for bufferedwrite commands.- CONFIG_SYS_FLASH_QUIET_TESTIf this option is defined, the common CFI flash doesn'tprint it's warning upon not recognized FLASH banks. Thisis useful, if some of the configured banks are onlyoptionally available.- CONFIG_FLASH_SHOW_PROGRESSIf defined (must be an integer), print out countdowndigits and dots.  Recommended value: 45 (9..1) for 80column displays, 15 (3..1) for 40 column displays.- CONFIG_FLASH_VERIFYIf defined, the content of the flash (destination) is comparedagainst the source after the write operation. An error messagewill be printed when the contents are not identical.Please note that this option is useless in nearly all cases,since such flash programming errors usually are detected earlierwhile unprotecting/erasing/programming. Please only enablethis option if you really know what you are doing.- CONFIG_SYS_RX_ETH_BUFFER:Defines the number of Ethernet receive buffers. On someEthernet controllers it is recommended to set this valueto 8 or even higher (EEPRO100 or 405 EMAC), since allbuffers can be full shortly after enabling the interfaceon high Ethernet traffic.Defaults to 4 if not defined.- CONFIG_ENV_MAX_ENTRIESMaximum number of entries in the hash table that is usedinternally to store the environment settings. The defaultsetting is supposed to be generous and should work in mostcases. This setting can be used to tune behaviour; seelib/hashtable.c for details.- CONFIG_ENV_FLAGS_LIST_DEFAULT- CONFIG_ENV_FLAGS_LIST_STATICEnable validation of the values given to environment variables whencalling env set.  Variables can be restricted to only decimal,hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,the variables can also be restricted to IP address or MAC address.The format of the list is:type_attribute = [s|d|x|b|i|m]access_attribute = [a|r|o|c]attributes = type_attribute[access_attribute]entry = variable_name[:attributes]list = entry[,list]The type attributes are:s - String (default)d - Decimalx - Hexadecimalb - Boolean ([1yYtT|0nNfF])i - IP addressm - MAC addressThe access attributes are:a - Any (default)r - Read-onlyo - Write-oncec - Change-default- CONFIG_ENV_FLAGS_LIST_DEFAULTDefine this to a list (string) to define the ".flags"environment variable in the default or embedded environment.- CONFIG_ENV_FLAGS_LIST_STATICDefine this to a list (string) to define validation thatshould be done if an entry is not found in the ".flags"environment variable.  To override a setting in the staticlist, simply add an entry for the same variable name to the".flags" variable.If CONFIG_REGEX is defined, the variable_name above is evaluated as aregular expression. This allows multiple variables to define the sameflags without explicitly listing them for each variable.- CONFIG_ENV_ACCESS_IGNORE_FORCEIf defined, don't allow the -f switch to env set override variableaccess flags.- CONFIG_SYS_GENERIC_BOARDThis selects the architecture-generic board system instead of thearchitecture-specific board files. It is intended to move boardsto this new framework over time. Defining this will disable thearch/foo/lib/board.c file and use common/board_f.c andcommon/board_r.c instead. To use this option your architecturemust support it (i.e. must select HAVE_GENERIC_BOARD in arch/Kconfig).If you find problems enabling this option on your board please reportthe problem and send patches!- CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC (OMAP only)This is set by OMAP boards for the max time that reset shouldbe asserted. See doc/README.omap-reset-time for details on howthe value can be calculated on a given board.- CONFIG_USE_STDINTIf stdint.h is available with your toolchain you can define thisoption to enable it. You can provide option 'USE_STDINT=1' whenbuilding U-Boot to enable this.The following definitions that deal with the placement and managementof environment data (variable area); in general, we support thefollowing configurations:- CONFIG_BUILD_ENVCRC:Builds up envcrc with the target environment so that external utilsmay easily extract it and embed it in final U-Boot images.- CONFIG_ENV_IS_IN_FLASH:Define this if the environment is in flash memory.a) The environment occupies one whole flash sector, which is   "embedded" in the text segment with the U-Boot code. This   happens usually with "bottom boot sector" or "top boot   sector" type flash chips, which have several smaller   sectors at the start or the end. For instance, such a   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In   such a case you would place the environment in one of the   4 kB sectors - with U-Boot code before and after it. With   "top boot sector" type flash chips, you would put the   environment in one of the last sectors, leaving a gap   between U-Boot and the environment.- CONFIG_ENV_OFFSET:   Offset of environment data (variable area) to the   beginning of flash memory; for instance, with bottom boot   type flash chips the second sector can be used: the offset   for this sector is given here.   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.- CONFIG_ENV_ADDR:   This is just another way to specify the start address of   the flash sector containing the environment (instead of   CONFIG_ENV_OFFSET).- CONFIG_ENV_SECT_SIZE:   Size of the sector containing the environment.b) Sometimes flash chips have few, equal sized, BIG sectors.   In such a case you don't want to spend a whole sector for   the environment.- CONFIG_ENV_SIZE:   If you use this in combination with CONFIG_ENV_IS_IN_FLASH   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part   of this flash sector for the environment. This saves   memory for the RAM copy of the environment.   It may also save flash memory if you decide to use this   when your environment is "embedded" within U-Boot code,   since then the remainder of the flash sector could be used   for U-Boot code. It should be pointed out that this is   STRONGLY DISCOURAGED from a robustness point of view:   updating the environment in flash makes it always   necessary to erase the WHOLE sector. If something goes   wrong before the contents has been restored from a copy in   RAM, your target system will be dead.- CONFIG_ENV_ADDR_REDUND  CONFIG_ENV_SIZE_REDUND   These settings describe a second storage area used to hold   a redundant copy of the environment data, so that there is   a valid backup copy in case there is a power failure during   a "saveenv" operation.BE CAREFUL! Any changes to the flash layout, and some changes to thesource code will make it necessary to adapt <board>/u-boot.lds*accordingly!- CONFIG_ENV_IS_IN_NVRAM:Define this if you have some non-volatile memory device(NVRAM, battery buffered SRAM) which you want to use for theenvironment.- CONFIG_ENV_ADDR:- CONFIG_ENV_SIZE:  These two #defines are used to determine the memory area you  want to use for environment. It is assumed that this memory  can just be read and written to, without any special  provision.BE CAREFUL! The first access to the environment happens quite earlyin U-Boot initialization (when we try to get the setting of for theconsole baudrate). You *MUST* have mapped your NVRAM area then, orU-Boot will hang.Please note that even with NVRAM we still use a copy of theenvironment in RAM: we could work on NVRAM directly, but we want tokeep settings there always unmodified except somebody uses "saveenv"to save the current settings.- CONFIG_ENV_IS_IN_EEPROM:Use this if you have an EEPROM or similar serial accessdevice and a driver for it.- CONFIG_ENV_OFFSET:- CONFIG_ENV_SIZE:  These two #defines specify the offset and size of the  environment area within the total memory of your EEPROM.- CONFIG_SYS_I2C_EEPROM_ADDR:  If defined, specified the chip address of the EEPROM device.  The default address is zero.- CONFIG_SYS_I2C_EEPROM_BUS:  If defined, specified the i2c bus of the EEPROM device.- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:  If defined, the number of bits used to address bytes in a  single page in the EEPROM device.  A 64 byte page, for example  would require six bits.- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:  If defined, the number of milliseconds to delay between  page writes.The default is zero milliseconds.- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:  The length in bytes of the EEPROM memory array address.  Note  that this is NOT the chip address length!- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:  EEPROM chips that implement "address overflow" are ones  like Catalyst 24WC04/08/16 which has 9/10/11 bits of  address and the extra bits end up in the "chip address" bit  slots. This makes a 24WC08 (1Kbyte) chip look like four 256  byte chips.  Note that we consider the length of the address field to  still be one byte because the extra address bits are hidden  in the chip address.- CONFIG_SYS_EEPROM_SIZE:  The size in bytes of the EEPROM device.- CONFIG_ENV_EEPROM_IS_ON_I2C  define this, if you have I2C and SPI activated, and your  EEPROM, which holds the environment, is on the I2C bus.- CONFIG_I2C_ENV_EEPROM_BUS  if you have an Environment on an EEPROM reached over  I2C muxes, you can define here, how to reach this  EEPROM. For example:  #define CONFIG_I2C_ENV_EEPROM_BUS  1  EEPROM which holds the environment, is reached over  a pca9547 i2c mux with address 0x70, channel 3.- CONFIG_ENV_IS_IN_DATAFLASH:Define this if you have a DataFlash memory device which youwant to use for the environment.- CONFIG_ENV_OFFSET:- CONFIG_ENV_ADDR:- CONFIG_ENV_SIZE:  These three #defines specify the offset and size of the  environment area within the total memory of your DataFlash placed  at the specified address.- CONFIG_ENV_IS_IN_SPI_FLASH:Define this if you have a SPI Flash memory device which youwant to use for the environment.- CONFIG_ENV_OFFSET:- CONFIG_ENV_SIZE:  These two #defines specify the offset and size of the  environment area within the SPI Flash. CONFIG_ENV_OFFSET must be  aligned to an erase sector boundary.- CONFIG_ENV_SECT_SIZE:  Define the SPI flash's sector size.- CONFIG_ENV_OFFSET_REDUND (optional):  This setting describes a second storage area of CONFIG_ENV_SIZE  size used to hold a redundant copy of the environment data, so  that there is a valid backup copy in case there is a power failure  during a "saveenv" operation. CONFIG_ENV_OFFSET_RENDUND must be  aligned to an erase sector boundary.- CONFIG_ENV_SPI_BUS (optional):- CONFIG_ENV_SPI_CS (optional):  Define the SPI bus and chip select. If not defined they will be 0.- CONFIG_ENV_SPI_MAX_HZ (optional):  Define the SPI max work clock. If not defined then use 1MHz.- CONFIG_ENV_SPI_MODE (optional):  Define the SPI work mode. If not defined then use SPI_MODE_3.- CONFIG_ENV_IS_IN_REMOTE:Define this if you have a remote memory space which youwant to use for the local device's environment.- CONFIG_ENV_ADDR:- CONFIG_ENV_SIZE:  These two #defines specify the address and size of the  environment area within the remote memory space. The  local device can get the environment from remote memory  space by SRIO or PCIE links.BE CAREFUL! For some special cases, the local device can not use"saveenv" command. For example, the local device will get theenvironment stored in a remote NOR flash by SRIO or PCIE link,but it can not erase, write this NOR flash by SRIO or PCIE interface.- CONFIG_ENV_IS_IN_NAND:Define this if you have a NAND device which you want to usefor the environment.- CONFIG_ENV_OFFSET:- CONFIG_ENV_SIZE:  These two #defines specify the offset and size of the environment  area within the first NAND device.  CONFIG_ENV_OFFSET must be  aligned to an erase block boundary.- CONFIG_ENV_OFFSET_REDUND (optional):  This setting describes a second storage area of CONFIG_ENV_SIZE  size used to hold a redundant copy of the environment data, so  that there is a valid backup copy in case there is a power failure  during a "saveenv" operation. CONFIG_ENV_OFFSET_RENDUND must be  aligned to an erase block boundary.- CONFIG_ENV_RANGE (optional):  Specifies the length of the region in which the environment  can be written.  This should be a multiple of the NAND device's  block size.  Specifying a range with more erase blocks than  are needed to hold CONFIG_ENV_SIZE allows bad blocks within  the range to be avoided.- CONFIG_ENV_OFFSET_OOB (optional):  Enables support for dynamically retrieving the offset of the  environment from block zero's out-of-band data.  The  "nand env.oob" command can be used to record this offset.  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when  using CONFIG_ENV_OFFSET_OOB.- CONFIG_NAND_ENV_DSTDefines address in RAM to which the nand_spl code should copy theenvironment. If redundant environment is used, it will be copied toCONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.- CONFIG_ENV_IS_IN_UBI:Define this if you have an UBI volume that you want to use for theenvironment.  This has the benefit of wear-leveling the environmentaccesses, which is important on NAND.- CONFIG_ENV_UBI_PART:  Define this to a string that is the mtd partition containing the UBI.- CONFIG_ENV_UBI_VOLUME:  Define this to the name of the volume that you want to store the  environment in.- CONFIG_ENV_UBI_VOLUME_REDUND:  Define this to the name of another volume to store a second copy of  the environment in.  This will enable redundant environments in UBI.  It is assumed that both volumes are in the same MTD partition.- CONFIG_UBI_SILENCE_MSG- CONFIG_UBIFS_SILENCE_MSG  You will probably want to define these to avoid a really noisy system  when storing the env in UBI.- CONFIG_ENV_IS_IN_FAT:       Define this if you want to use the FAT file system for the environment.       - FAT_ENV_INTERFACE:         Define this to a string that is the name of the block device.       - FAT_ENV_DEV_AND_PART:         Define this to a string to specify the partition of the device. It can         be as following:           "D:P", "D:0", "D", "D:" or "D:auto" (D, P are integers. And P >= 1)               - "D:P": device D partition P. Error occurs if device D has no                        partition table.               - "D:0": device D.               - "D" or "D:": device D partition 1 if device D has partition                              table, or the whole device D if has no partition                              table.               - "D:auto": first partition in device D with bootable flag set.                           If none, first valid partition in device D. If no                           partition table then means device D.       - FAT_ENV_FILE:         It's a string of the FAT file name. This file use to store the         environment.       - CONFIG_FAT_WRITE:         This should be defined. Otherwise it cannot save the environment file.- CONFIG_ENV_IS_IN_MMC:Define this if you have an MMC device which you want to use for theenvironment.- CONFIG_SYS_MMC_ENV_DEV:  Specifies which MMC device the environment is stored in.- CONFIG_SYS_MMC_ENV_PART (optional):  Specifies which MMC partition the environment is stored in. If not  set, defaults to partition 0, the user area. Common values might be  1 (first MMC boot partition), 2 (second MMC boot partition).- CONFIG_ENV_OFFSET:- CONFIG_ENV_SIZE:  These two #defines specify the offset and size of the environment  area within the specified MMC device.  If offset is positive (the usual case), it is treated as relative to  the start of the MMC partition. If offset is negative, it is treated  as relative to the end of the MMC partition. This can be useful if  your board may be fitted with different MMC devices, which have  different sizes for the MMC partitions, and you always want the  environment placed at the very end of the partition, to leave the  maximum possible space before it, to store other data.  These two values are in units of bytes, but must be aligned to an  MMC sector boundary.- CONFIG_ENV_OFFSET_REDUND (optional):  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to  hold a redundant copy of the environment data. This provides a  valid backup copy in case the other copy is corrupted, e.g. due  to a power failure during a "saveenv" operation.  This value may also be positive or negative; this is handled in the  same way as CONFIG_ENV_OFFSET.  This value is also in units of bytes, but must also be aligned to  an MMC sector boundary.- CONFIG_ENV_SIZE_REDUND (optional):  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is  set. If this value is set, it must be set to the same value as  CONFIG_ENV_SIZE.- CONFIG_SYS_SPI_INIT_OFFSETDefines offset to the initial SPI buffer area in DPRAM. Thearea is used at an early stage (ROM part) if the environmentis configured to reside in the SPI EEPROM: We need a 520 bytescratch DPRAM area. It is used between the two initializationcalls (spi_init_f() and spi_init_r()). A value of 0xB00 seemsto be a good choice since it makes it far enough from thestart of the data area as well as from the stack pointer.Please note that the environment is read-only until the monitorhas been relocated to RAM and a RAM copy of the environment has beencreated; also, when using EEPROM you will have to use getenv_f()until then to read environment variables.The environment is protected by a CRC32 checksum. Before the monitoris relocated into RAM, as a result of a bad CRC you will be workingwith the compiled-in default environment - *silently*!!! [This isnecessary, because the first environment variable we need is the"baudrate" setting for the console - if we have a bad CRC, we don'thave any device yet where we could complain.]Note: once the monitor has been relocated, then it will complain ifthe default environment is used; a new CRC is computed as soon as youuse the "saveenv" command to store a valid environment.- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:Echo the inverted Ethernet link state to the fault LED.Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR      also needs to be defined.- CONFIG_SYS_FAULT_MII_ADDR:MII address of the PHY to check for the Ethernet link state.- CONFIG_NS16550_MIN_FUNCTIONS:Define this if you desire to only have use of the NS16550_initand NS16550_putc functions for the serial driver located atdrivers/serial/ns16550.c.  This option is useful for savingspace for already greatly restricted images, including but notlimited to NAND_SPL configurations.- CONFIG_DISPLAY_BOARDINFODisplay information about the board that U-Boot is running onwhen U-Boot starts up. The board function checkboard() is calledto do this.- CONFIG_DISPLAY_BOARDINFO_LATESimilar to the previous option, but display this informationlater, once stdio is running and output goes to the LCD, ifpresent.- CONFIG_BOARD_SIZE_LIMIT:Maximum size of the U-Boot image. When defined, thebuild system checks that the actual size does notexceed it.Low Level (hardware related) configuration options:---------------------------------------------------- CONFIG_SYS_CACHELINE_SIZE:Cache Line Size of the CPU.- CONFIG_SYS_DEFAULT_IMMR:Default address of the IMMR after system reset.Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,and RPXsuper) to be able to adjust the position ofthe IMMR register after a reset.- CONFIG_SYS_CCSRBAR_DEFAULT:Default (power-on reset) physical address of CCSR on FreescalePowerPC SOCs.- CONFIG_SYS_CCSRBAR:Virtual address of CCSR.  On a 32-bit build, this is typicallythe same value as CONFIG_SYS_CCSRBAR_DEFAULT.CONFIG_SYS_DEFAULT_IMMR must also be set to this value,for cross-platform code that uses that macro instead.- CONFIG_SYS_CCSRBAR_PHYS:Physical address of CCSR.  CCSR can be relocated to a newphysical address, if desired.  In this case, this macro shouldbe set to that address. Otherwise, it should be set to thesame value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSRis typically relocated on 36-bit builds.  It is recommendedthat this macro be defined via the _HIGH and _LOW macros:#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)- CONFIG_SYS_CCSRBAR_PHYS_HIGH:Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.This value is typicallyeither 0 (32-bit build) or 0xF (36-bit build).This macro isused in assembly code, so it must not contain typecasts orinteger size suffixes (e.g. "ULL").- CONFIG_SYS_CCSRBAR_PHYS_LOW:Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro isused in assembly code, so it must not contain typecasts orinteger size suffixes (e.g. "ULL").- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will beforced to a value that ensures that CCSR is not relocated.- Floppy Disk Support:CONFIG_SYS_FDC_DRIVE_NUMBERthe default drive number (default value 0)CONFIG_SYS_ISA_IO_STRIDEdefines the spacing between FDC chipset registers(default value 1)CONFIG_SYS_ISA_IO_OFFSETdefines the offset of register from address. Itdepends on which part of the data bus is connected tothe FDC chipset. (default value 0)If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET andCONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take theirdefault value.if CONFIG_SYS_FDC_HW_INIT is defined, then the functionfdc_hw_init() is called at the beginning of the FDCsetup. fdc_hw_init() must be provided by the boardsource code. It is used to make hardware-dependentinitializations.- CONFIG_IDE_AHB:Most IDE controllers were designed to be connected with PCIinterface. Only few of them were designed for AHB interface.When software is doing ATA command and data transfer toIDE devices through IDE-AHB controller, some additionalregisters accessing to these kind of IDE-AHB controlleris required.- CONFIG_SYS_IMMR:Physical address of the Internal Memory.DO NOT CHANGE unless you know exactly what you'redoing! (11-4) [MPC8xx/82xx systems only]- CONFIG_SYS_INIT_RAM_ADDR:Start address of memory area that can be used forinitial data and stack; please note that this must bewritable memory that is working WITHOUT specialinitialization, i. e. you CANNOT use normal RAM whichwill become available only after programming thememory controller and running certain initializationsequences.U-Boot uses the following memory types:- MPC8xx and MPC8260: IMMR (internal memory of the CPU)- MPC824X: data cache- PPC4xx:  data cache- CONFIG_SYS_GBL_DATA_OFFSET:Offset of the initial data structure in the memoryarea defined by CONFIG_SYS_INIT_RAM_ADDR. UsuallyCONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initialdata is located at the end of the available space(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is justbelow that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +CONFIG_SYS_GBL_DATA_OFFSET) downward.Note:On the MPC824X (or other systems that use the datacache for initial memory) the address chosen forCONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it mustpoint to an otherwise UNUSED address space betweenthe top of RAM and the start of the PCI space.- CONFIG_SYS_SIUMCR:SIU Module Configuration (11-6)- CONFIG_SYS_SYPCR:System Protection Control (11-9)- CONFIG_SYS_TBSCR:Time Base Status and Control (11-26)- CONFIG_SYS_PISCR:Periodic Interrupt Status and Control (11-31)- CONFIG_SYS_PLPRCR:PLL, Low-Power, and Reset Control Register (15-30)- CONFIG_SYS_SCCR:System Clock and reset Control Register (15-27)- CONFIG_SYS_OR_TIMING_SDRAM:SDRAM timing- CONFIG_SYS_MAMR_PTA:periodic timer for refresh- CONFIG_SYS_DER:Debug Event Register (37-47)- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,  CONFIG_SYS_BR1_PRELIM:Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:Machine Mode Register and Memory Periodic TimerPrescaler definitions (SDRAM timing)- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:enable I2C microcode relocation patch (MPC8xx);define relocation offset in DPRAM [DSP2]- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:enable SMC microcode relocation patch (MPC8xx);define relocation offset in DPRAM [SMC1]- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:enable SPI microcode relocation patch (MPC8xx);define relocation offset in DPRAM [SCC4]- CONFIG_SYS_USE_OSCCLK:Use OSCM clock mode on MBX8xx board. Be careful,wrong setting might damage your board. Readdoc/README.MBX before setting this variable!- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)Offset of the bootmode word in DPRAM used by post(Power On Self Tests). This definition overrides#define'd default value in commproc.h resp.cpm_8260.h.- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.- CONFIG_PCI_DISABLE_PCIE:Disable PCI-Express on systems where it is supported but notrequired.- CONFIG_PCI_ENUM_ONLYOnly scan through and get the devices on the buses.Don't do any setup work, presumably because someone orsomething has already done it, and we don't need to do ita second time.Useful for platforms that are pre-bootedby coreboot or similar.- CONFIG_PCI_INDIRECT_BRIDGE:Enable support for indirect PCI bridges.- CONFIG_SYS_SRIO:Chip has SRIO or not- CONFIG_SRIO1:Board has SRIO 1 port available- CONFIG_SRIO2:Board has SRIO 2 port available- CONFIG_SRIO_PCIE_BOOT_MASTERBoard can support master function for Boot from SRIO and PCIE- CONFIG_SYS_SRIOn_MEM_VIRT:Virtual Address of SRIO port 'n' memory region- CONFIG_SYS_SRIOn_MEM_PHYS:Physical Address of SRIO port 'n' memory region- CONFIG_SYS_SRIOn_MEM_SIZE:Size of SRIO port 'n' memory region- CONFIG_SYS_NAND_BUSWIDTH_16BITDefined to tell the NAND controller that the NAND chip is usinga 16 bit bus.Not all NAND drivers use this symbol.Example of drivers that use it:- drivers/mtd/nand/ndfc.c- drivers/mtd/nand/mxc_nand.c- CONFIG_SYS_NDFC_EBC0_CFGSets the EBC0_CFG register for the NDFC. If not defineda default value will be used.- CONFIG_SPD_EEPROMGet DDR timing information from an I2C EEPROM. Commonwith pluggable memory modules such as SODIMMs  SPD_EEPROM_ADDRESSI2C address of the SPD EEPROM- CONFIG_SYS_SPD_BUS_NUMIf SPD EEPROM is on an I2C bus other than the firstone, specify here. Note that the value must resolveto something your driver can deal with.- CONFIG_SYS_DDR_RAW_TIMINGGet DDR timing information from other than SPD. Common withsoldered DDR chips onboard without SPD. DDR raw timingparameters are extracted from datasheet and hard-coded intoheader files or board specific files.- CONFIG_FSL_DDR_INTERACTIVEEnable interactive DDR debugging. See doc/README.fsl-ddr.- CONFIG_FSL_DDR_SYNC_REFRESHEnable sync of refresh for multiple controllers.- CONFIG_FSL_DDR_BISTEnable built-in memory test for Freescale DDR controllers.- CONFIG_SYS_83XX_DDR_USES_CS0Only for 83xx systems. If specified, then DDR shouldbe configured using CS0 and CS1 instead of CS2 and CS3.- CONFIG_ETHER_ON_FEC[12]Define to enable FEC[12] on a 8xx series processor.- CONFIG_FEC[12]_PHYDefine to the hardcoded PHY address which correspondsto the given FEC; i. e.#define CONFIG_FEC1_PHY 4means that the PHY with address 4 is connected to FEC1When set to -1, means to probe for first available.- CONFIG_FEC[12]_PHY_NORXERRThe PHY does not have a RXERR line (RMII only).(so program the FEC to ignore it).- CONFIG_RMIIEnable RMII mode for all FECs.Note that this is a global option, we can'thave one FEC in standard MII mode and another in RMII mode.- CONFIG_CRC32_VERIFYAdd a verify option to the crc32 command.The syntax is:=> crc32 -v <address> <count> <crc32>Where address/count indicate a memory areaand crc32 is the correct crc32 which thearea should have.- CONFIG_LOOPWAdd the "loopw" memory command. This only takes effect ifthe memory commands are activated globally (CONFIG_CMD_MEM).- CONFIG_MX_CYCLICAdd the "mdc" and "mwc" memory commands. These are cyclic"md/mw" commands.Examples:=> mdc.b 10 4 500This command will print 4 bytes (10,11,12,13) each 500 ms.=> mwc.l 100 12345678 10This command will write 12345678 to address 100 all 10 ms.This only takes effect if the memory commands are activatedglobally (CONFIG_CMD_MEM).- CONFIG_SKIP_LOWLEVEL_INIT[ARM, NDS32, MIPS only] If this variable is defined, then certainlow level initializations (like setting up the memorycontroller) are omitted and/or U-Boot does notrelocate itself into RAM.Normally this variable MUST NOT be defined. The onlyexception is when U-Boot is loaded (to RAM) by someother boot loader or by a debugger which performsthese initializations itself.- CONFIG_SPL_BUILDModifies the behaviour of start.S when compiling a loaderthat is executed before the actual U-Boot. E.g. whencompiling a NAND SPL.- CONFIG_TPL_BUILDModifies the behaviour of start.S  when compiling a loaderthat is executed after the SPL and before the actual U-Boot.It is loaded by the SPL.- CONFIG_SYS_MPC85XX_NO_RESETVECOnly for 85xx systems. If this variable is specified, the section.resetvec is not kept and the section .bootpg is placed in theprevious 4k of the .text section.- CONFIG_ARCH_MAP_SYSMEMGenerally U-Boot (and in particular the md command) useseffective address. It is therefore not necessary to regardU-Boot address as virtual addresses that need to be translatedto physical addresses. However, sandbox requires this, sinceit maintains its own little RAM buffer which contains alladdressable memory. This option causes some memory accessesto be mapped through map_sysmem() / unmap_sysmem().- CONFIG_USE_ARCH_MEMCPY  CONFIG_USE_ARCH_MEMSETIf these options are used a optimized version of memcpy/memset willbe used if available. These functions may be faster under someconditions but may increase the binary size.- CONFIG_X86_RESET_VECTORIf defined, the x86 reset vector code is included. This is notneeded when U-Boot is running from Coreboot.- CONFIG_SYS_MPUCLKDefines the MPU clock speed (in MHz).NOTE : currently only supported on AM335x platforms.- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:Enables the RTC32K OSC on AM33xx based plattforms- CONFIG_SYS_NAND_NO_SUBPAGE_WRITEOption to disable subpage write in NAND driverdriver that uses this:drivers/mtd/nand/davinci_nand.cFreescale QE/FMAN Firmware Support:-----------------------------------The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support theloading of "firmware", which is encoded in the QE firmware binary format.This firmware often needs to be loaded during U-Boot booting, so macrosare used to identify the storage device (NOR flash, SPI, etc) and the addresswithin that device.- CONFIG_SYS_FMAN_FW_ADDRThe address in the storage device where the FMAN microcode is located.  Themeaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macrois also specified.- CONFIG_SYS_QE_FW_ADDRThe address in the storage device where the QE microcode is located.  Themeaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macrois also specified.- CONFIG_SYS_QE_FMAN_FW_LENGTHThe maximum possible size of the firmware.  The firmware binary formathas a field that specifies the actual size of the firmware, but itmight not be possible to read any part of the firmware unless somelocal storage is allocated to hold the entire firmware first.- CONFIG_SYS_QE_FMAN_FW_IN_NORSpecifies that QE/FMAN firmware is located in NOR flash, mapped asnormal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is thevirtual address in NOR flash.- CONFIG_SYS_QE_FMAN_FW_IN_NANDSpecifies that QE/FMAN firmware is located in NAND flash.CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.- CONFIG_SYS_QE_FMAN_FW_IN_MMCSpecifies that QE/FMAN firmware is located on the primary SD/MMCdevice.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.- CONFIG_SYS_QE_FMAN_FW_IN_SPIFLASHSpecifies that QE/FMAN firmware is located on the primary SPIdevice.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.- CONFIG_SYS_QE_FMAN_FW_IN_REMOTESpecifies that QE/FMAN firmware is located in the remote (master)memory space.CONFIG_SYS_FMAN_FW_ADDR is a virtual address whichcan be mapped from slave TLB->slave LAW->slave SRIO or PCIE outboundwindow->master inbound window->master LAW->the ucode address inmaster's memory space.Freescale Layerscape Management Complex Firmware Support:---------------------------------------------------------The Freescale Layerscape Management Complex (MC) supports the loading of"firmware".This firmware often needs to be loaded during U-Boot booting, so macrosare used to identify the storage device (NOR flash, SPI, etc) and the addresswithin that device.- CONFIG_FSL_MC_ENETEnable the MC driver for Layerscape SoCs.- CONFIG_SYS_LS_MC_FW_ADDRThe address in the storage device where the firmware is located.  Themeaning of this address depends on which CONFIG_SYS_LS_MC_FW_IN_xxx macrois also specified.- CONFIG_SYS_LS_MC_FW_LENGTHThe maximum possible size of the firmware.  The firmware binary formathas a field that specifies the actual size of the firmware, but itmight not be possible to read any part of the firmware unless somelocal storage is allocated to hold the entire firmware first.- CONFIG_SYS_LS_MC_FW_IN_NORSpecifies that MC firmware is located in NOR flash, mapped asnormal addressable memory via the LBC. CONFIG_SYS_LS_MC_FW_ADDR is thevirtual address in NOR flash.Freescale Layerscape Debug Server Support:-------------------------------------------The Freescale Layerscape Debug Server Support supports the loading of"Debug Server firmware" and triggering SP boot-rom.This firmware often needs to be loaded during U-Boot booting.- CONFIG_FSL_DEBUG_SERVEREnable the Debug Server for Layerscape SoCs.- CONFIG_SYS_DEBUG_SERVER_DRAM_BLOCK_MIN_SIZEDefine minimum DDR size required for debug server image- CONFIG_SYS_MEM_TOP_HIDE_MINDefine minimum DDR size to be hided from top of the DDR memoryReproducible builds-------------------In order to achieve reproducible builds, timestamps used in the U-Boot buildprocess have to be set to a fixed value.This is done using the SOURCE_DATE_EPOCH environment variable.SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configurationoption for U-Boot or an environment variable in U-Boot.SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.Building the Software:======================Building U-Boot has been tested in several native build environmentsand in many different cross environments. Of course we cannot supportall possibly existing versions of cross development tools in all(potentially obsolete) versions. In case of tool chain problems werecommend to use the ELDK (seehttp://www.denx.de/wiki/DULG/ELDK)which is extensively used to build and test U-Boot.If you are not using a native environment, it is assumed that youhave GNU cross compiling tools available in your path. In this case,you must set the environment variable CROSS_COMPILE in your shell.Note that no changes to the Makefile or any other source files arenecessary. For example using the ELDK on a 4xx CPU, please enter:$ CROSS_COMPILE=ppc_4xx-$ export CROSS_COMPILENote: If you wish to generate Windows versions of the utilities in      the tools directory you can use the MinGW toolchain      (http://www.mingw.org).  Set your HOST tools to the MinGW      toolchain and execute 'make tools'.  For example:       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools      Binaries such as tools/mkimage.exe will be created which can      be executed on computers running Windows.U-Boot is intended to be simple to build. After installing thesources you must configure U-Boot for one specific board type. Thisis done by typing:make NAME_defconfigwhere "NAME_defconfig" is the name of one of the existing configu-rations; see boards.cfg for supported names.Note: for some board special configuration names may exist; check if      additional information is available from the board vendor; for      instance, the TQM823L systems are available without (standard)      or with LCD support. You can select such additional "features"      when choosing the configuration, i. e.      make TQM823L_defconfig- will configure for a plain TQM823L, i. e. no LCD support      make TQM823L_LCD_defconfig- will configure for a TQM823L with U-Boot console on LCD      etc.Finally, type "make all", and you should get some working U-Bootimages ready for download to / installation on your system:- "u-boot.bin" is a raw binary image- "u-boot" is an image in ELF binary format- "u-boot.srec" is in Motorola S-Record formatBy default the build is performed locally and the objects are savedin the source directory. One of the two methods can be used to changethis behavior and build U-Boot to some external directory:1. Add O= to the make command line invocations:make O=/tmp/build distcleanmake O=/tmp/build NAME_defconfigmake O=/tmp/build all2. Set environment variable KBUILD_OUTPUT to point to the desired location:export KBUILD_OUTPUT=/tmp/buildmake distcleanmake NAME_defconfigmake allNote that the command line "O=" setting overrides the KBUILD_OUTPUT environmentvariable.Please be aware that the Makefiles assume you are using GNU make, sofor instance on NetBSD you might need to use "gmake" instead ofnative "make".If the system board that you have is not listed, then you will needto port U-Boot to your hardware platform. To do this, follow thesesteps:1.  Add a new configuration option for your board to the toplevel    "boards.cfg" file, using the existing entries as examples.    Follow the instructions there to keep the boards in order.2.  Create a new directory to hold your board specific code. Add any    files you need. In your board directory, you will need at least    the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".3.  Create a new configuration file "include/configs/<board>.h" for    your board3.  If you're porting U-Boot to a new CPU, then also create a new    directory to hold your CPU specific code. Add any files you need.4.  Run "make <board>_defconfig" with your new name.5.  Type "make", and you should get a working "u-boot.srec" file    to be installed on your target system.6.  Debug and solve any problems that might arise.    [Of course, this last step is much harder than it sounds.]Testing of U-Boot Modifications, Ports to New Hardware, etc.:==============================================================If you have modified U-Boot sources (for instance added a new boardor support for new devices, a new CPU, etc.) you are expected toprovide feedback to the other developers. The feedback normally takesthe form of a "patch", i. e. a context diff against a certain (latestofficial or latest in the git repository) version of U-Boot sources.But before you submit such a patch, please verify that your modifi-cation did not break existing code. At least make sure that *ALL* ofthe supported boards compile WITHOUT ANY compiler warnings. To do so,just run the "MAKEALL" script, which will configure and build U-Bootfor ALL supported system. Be warned, this will take a while. You canselect which (cross) compiler to use by passing a `CROSS_COMPILE'environment variable to the script, i. e. to use the ELDK cross toolsyou can typeCROSS_COMPILE=ppc_8xx- MAKEALLor to build on a native PowerPC system you can typeCROSS_COMPILE=' ' MAKEALLWhen using the MAKEALL script, the default behaviour is to buildU-Boot in the source directory. This location can be changed bysetting the BUILD_DIR environment variable. Also, for each targetbuilt, the MAKEALL script saves two log files (<target>.ERR and<target>.MAKEALL) in the <source dir>/LOG directory. This defaultlocation can be changed by setting the MAKEALL_LOGDIR environmentvariable. For example:export BUILD_DIR=/tmp/buildexport MAKEALL_LOGDIR=/tmp/logCROSS_COMPILE=ppc_8xx- MAKEALLWith the above settings build objects are saved in the /tmp/build,log files are saved in the /tmp/log and the source tree remains cleanduring the whole build process.See also "U-Boot Porting Guide" below.Monitor Commands - Overview:============================go- start application at address 'addr'run- run commands in an environment variablebootm- boot application image from memorybootp- boot image via network using BootP/TFTP protocolbootz   - boot zImage from memorytftpboot- boot image via network using TFTP protocol       and env variables "ipaddr" and "serverip"       (and eventually "gatewayip")tftpput - upload a file via network using TFTP protocolrarpboot- boot image via network using RARP/TFTP protocoldiskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'loads- load S-Record file over serial lineloadb- load binary file over serial line (kermit mode)md- memory displaymm- memory modify (auto-incrementing)nm- memory modify (constant address)mw- memory write (fill)cp- memory copycmp- memory comparecrc32- checksum calculationi2c- I2C sub-systemsspi- SPI utility commandsbase- print or set address offsetprintenv- print environment variablessetenv- set environment variablessaveenv - save environment variables to persistent storageprotect - enable or disable FLASH write protectionerase- erase FLASH memoryflinfo- print FLASH memory informationnand- NAND memory operations (see doc/README.nand)bdinfo- print Board Info structureiminfo- print header information for application imageconinfo - print console devices and informationside- IDE sub-systemloop- infinite loop on address rangeloopw- infinite write loop on address rangemtest- simple RAM testicache- enable or disable instruction cachedcache- enable or disable data cachereset- Perform RESET of the CPUecho- echo args to consoleversion - print monitor versionhelp- print online help?- alias for 'help'Monitor Commands - Detailed Description:========================================TODO.For now: just type "help <command>".Environment Variables:======================U-Boot supports user configuration using Environment Variables whichcan be made persistent by saving to Flash memory.Environment Variables are set using "setenv", printed using"printenv", and saved to Flash using "saveenv". Using "setenv"without a value can be used to delete a variable from theenvironment. As long as you don't save the environment you areworking with an in-memory copy. In case the Flash area containing theenvironment is erased by accident, a default environment is provided.Some configuration options can be set using Environment Variables.List of environment variables (most likely not complete):  baudrate- see CONFIG_BAUDRATE  bootdelay- see CONFIG_BOOTDELAY  bootcmd- see CONFIG_BOOTCOMMAND  bootargs- Boot arguments when booting an RTOS image  bootfile- Name of the image to load with TFTP  bootm_low- Memory range available for image processing in the bootm  command can be restricted. This variable is given as  a hexadecimal number and defines lowest address allowed  for use by the bootm command. See also "bootm_size"  environment variable. Address defined by "bootm_low" is  also the base of the initial memory mapping for the Linux  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and  bootm_mapsize.  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.  This variable is given as a hexadecimal number and it  defines the size of the memory region starting at base  address bootm_low that is accessible by the Linux kernel  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used  as the default value if it is defined, and bootm_size is  used otherwise.  bootm_size- Memory range available for image processing in the bootm  command can be restricted. This variable is given as  a hexadecimal number and defines the size of the region  allowed for use by the bootm command. See also "bootm_low"  environment variable.  updatefile- Location of the software update file on a TFTP server, used  by the automatic software update feature. Please refer to  documentation in doc/README.update for more details.  autoload- if set to "no" (any string beginning with 'n'),  "bootp" will just load perform a lookup of the  configuration from the BOOTP server, but not try to  load any image using TFTP  autostart- if set to "yes", an image loaded using the "bootp",  "rarpboot", "tftpboot" or "diskboot" commands will  be automatically started (by internally calling  "bootm")  If set to "no", a standalone image passed to the  "bootm" command will be copied to the load address  (and eventually uncompressed), but NOT be started.  This can be used to load and uncompress arbitrary  data.  fdt_high- if set this restricts the maximum address that the  flattened device tree will be copied into upon boot.  For example, if you have a system with 1 GB memory  at physical address 0x10000000, while Linux kernel  only recognizes the first 704 MB as low memory, you  may need to set fdt_high as 0x3C000000 to have the  device tree blob be copied to the maximum address  of the 704 MB low memory, so that Linux kernel can  access it during the boot procedure.  If this is set to the special value 0xFFFFFFFF then  the fdt will not be copied at all on boot.  For this  to work it must reside in writable memory, have  sufficient padding on the end of it for u-boot to  add the information it needs into it, and the memory  must be accessible by the kernel.  fdtcontroladdr- if set this is the address of the control flattened  device tree used by U-Boot when CONFIG_OF_CONTROL is  defined.  i2cfast- (PPC405GP|PPC405EP only)  if set to 'y' configures Linux I2C driver for fast  mode (400kHZ). This environment variable is used in  initialization code. So, for changes to be effective  it must be saved and board must be reset.  initrd_high- restrict positioning of initrd images:  If this variable is not set, initrd images will be  copied to the highest possible address in RAM; this  is usually what you want since it allows for  maximum initrd size. If for some reason you want to  make sure that the initrd image is loaded below the  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment  variable to a value of "no" or "off" or "0".  Alternatively, you can set it to a maximum upper  address to use (U-Boot will still check that it  does not overwrite the U-Boot stack and data).  For instance, when you have a system with 16 MB  RAM, and want to reserve 4 MB from use by Linux,  you can do this by adding "mem=12M" to the value of  the "bootargs" variable. However, now you must make  sure that the initrd image is placed in the first  12 MB as well - this can be done with  setenv initrd_high 00c00000  If you set initrd_high to 0xFFFFFFFF, this is an  indication to U-Boot that all addresses are legal  for the Linux kernel, including addresses in flash  memory. In this case U-Boot will NOT COPY the  ramdisk at all. This may be useful to reduce the  boot time on your system, but requires that this  feature is supported by your Linux kernel.  ipaddr- IP address; needed for tftpboot command  loadaddr- Default load address for commands like "bootp",  "rarpboot", "tftpboot", "loadb" or "diskboot"  loads_echo- see CONFIG_LOADS_ECHO  serverip- TFTP server IP address; needed for tftpboot command  bootretry- see CONFIG_BOOT_RETRY_TIME  bootdelaykey- see CONFIG_AUTOBOOT_DELAY_STR  bootstopkey- see CONFIG_AUTOBOOT_STOP_STR  ethprime- controls which interface is used first.  ethact- controls which interface is currently active.  For example you can do the following  => setenv ethact FEC  => ping 192.168.0.1 # traffic sent on FEC  => setenv ethact SCC  => ping 10.0.0.1 # traffic sent on SCC  ethrotate- When set to "no" U-Boot does not go through all  available network interfaces.  It just stays at the currently selected interface.  netretry- When set to "no" each network operation will  either succeed or fail without retrying.  When set to "once" the network operation will  fail when all the available network interfaces  are tried once without success.  Useful on scripts which control the retry operation  themselves.  npe_ucode- set load address for the NPE microcode  silent_linux  - If set then Linux will be told to boot silently, by  changing the console to be empty. If "yes" it will be  made silent. If "no" it will not be made silent. If  unset, then it will be made silent if the U-Boot console  is silent.  tftpsrcp- If this is set, the value is used for TFTP's  UDP source port.  tftpdstp- If this is set, the value is used for TFTP's UDP  destination port instead of the Well Know Port 69.  tftpblocksize - Block size to use for TFTP transfers; if not set,  we use the TFTP server's default block size  tftptimeout- Retransmission timeout for TFTP packets (in milli-  seconds, minimum value is 1000 = 1 second). Defines  when a packet is considered to be lost so it has to  be retransmitted. The default is 5000 = 5 seconds.  Lowering this value may make downloads succeed  faster in networks with high packet loss rates or  with unreliable TFTP servers.  tftptimeoutcountmax- maximum count of TFTP timeouts (no  unit, minimum value = 0). Defines how many timeouts  can happen during a single file transfer before that  transfer is aborted. The default is 10, and 0 means  'no timeouts allowed'. Increasing this value may help  downloads succeed with high packet loss rates, or with  unreliable TFTP servers or client hardware.  vlan- When set to a value < 4095 the traffic over  Ethernet is encapsulated/received over 802.1q  VLAN tagged frames.The following image location variables contain the location of imagesused in booting. The "Image" column gives the role of the image and isnot an environment variable name. The other columns are environmentvariable names. "File Name" gives the name of the file on a TFTPserver, "RAM Address" gives the location in RAM the image will beloaded to, and "Flash Location" gives the image's address in NORflash or offset in NAND flash.*Note* - these variables don't have to be defined for all boards, someboards currently use other variables for these purposes, and someboards use these variables for other purposes.Image    File Name     RAM Address       Flash Location-----    ---------     -----------       --------------u-boot    u-boot     u-boot_addr_r     u-boot_addrLinux kernel    bootfile     kernel_addr_r     kernel_addrdevice tree blob    fdtfile     fdt_addr_r       fdt_addrramdisk    ramdiskfile     ramdisk_addr_r    ramdisk_addrThe following environment variables may be used and automaticallyupdated by the network boot commands ("bootp" and "rarpboot"),depending the information provided by your boot server:  bootfile- see above  dnsip- IP address of your Domain Name Server  dnsip2- IP address of your secondary Domain Name Server  gatewayip- IP address of the Gateway (Router) to use  hostname- Target hostname  ipaddr- see above  netmask- Subnet Mask  rootpath- Pathname of the root filesystem on the NFS server  serverip- see aboveThere are two special Environment Variables:  serial#- contains hardware identification information such  as type string and/or serial number  ethaddr- Ethernet addressThese variables can be set only once (usually during manufacturing ofthe board). U-Boot refuses to delete or overwrite these variablesonce they have been set once.Further special Environment Variables:  ver- Contains the U-Boot version string as printed  with the "version" command. This variable is  readonly (see CONFIG_VERSION_VARIABLE).Please note that changes to some configuration parameters may takeonly effect after the next boot (yes, that's just like Windoze :-).Callback functions for environment variables:---------------------------------------------For some environment variables, the behavior of u-boot needs to changewhen their values are changed.  This functionality allows functions tobe associated with arbitrary variables.  On creation, overwrite, ordeletion, the callback will provide the opportunity for some sideeffect to happen or for the change to be rejected.The callbacks are named and associated with a function using theU_BOOT_ENV_CALLBACK macro in your board or driver code.These callbacks are associated with variables in one of two ways.  Thestatic list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATICin the board configuration to a string that defines a list ofassociations.  The list must be in the following format:entry = variable_name[:callback_name]list = entry[,list]If the callback name is not specified, then the callback is deleted.Spaces are also allowed anywhere in the list.Callbacks can also be associated by defining the ".callbacks" variablewith the same list format above.  Any association in ".callbacks" willoverride any association in the static list. You can defineCONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the".callbacks" environment variable in the default or embedded environment.If CONFIG_REGEX is defined, the variable_name above is evaluated as aregular expression. This allows multiple variables to be connected tothe same callback without explicitly listing them all out.Command Line Parsing:=====================There are two different command line parsers available with U-Boot:the old "simple" one, and the much more powerful "hush" shell:Old, simple command line parser:--------------------------------- supports environment variables (through setenv / saveenv commands)- several commands on one line, separated by ';'- variable substitution using "... ${name} ..." syntax- special characters ('$', ';') can be escaped by prefixing with '\',  for example:setenv bootcmd bootm \${address}- You can also escape text by enclosing in single apostrophes, for example:setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'Hush shell:------------ similar to Bourne shell, with control structures like  if...then...else...fi, for...do...done; while...do...done,  until...do...done, ...- supports environment ("global") variables (through setenv / saveenv  commands) and local shell variables (through standard shell syntax  "name=value"); only environment variables can be used with "run"  commandGeneral rules:--------------(1) If a command line (or an environment variable executed by a "run"    command) contains several commands separated by semicolon, and    one of these commands fails, then the remaining commands will be    executed anyway.(2) If you execute several variables with one call to run (i. e.    calling run with a list of variables as arguments), any failing    command will cause "run" to terminate, i. e. the remaining    variables are not executed.Note for Redundant Ethernet Interfaces:=======================================Some boards come with redundant Ethernet interfaces; U-Boot supportssuch configurations and is capable of automatic selection of a"working" interface when needed. MAC assignment works as follows:Network interfaces are numbered eth0, eth1, eth2, ... CorrespondingMAC addresses can be stored in the environment as "ethaddr" (=>eth0),"eth1addr" (=>eth1), "eth2addr", ...If the network interface stores some valid MAC address (for instancein SROM), this is used as default address if there is NO correspon-ding setting in the environment; if the corresponding environmentvariable is set, this overrides the settings in the card; that means:o If the SROM has a valid MAC address, and there is no address in the  environment, the SROM's address is used.o If there is no valid address in the SROM, and a definition in the  environment exists, then the value from the environment variable is  used.o If both the SROM and the environment contain a MAC address, and  both addresses are the same, this MAC address is used.o If both the SROM and the environment contain a MAC address, and the  addresses differ, the value from the environment is used and a  warning is printed.o If neither SROM nor the environment contain a MAC address, an error  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case  a random, locally-assigned MAC is used.If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresseswill be programmed into hardware as part of the initialization process. Thismay be skipped by setting the appropriate 'ethmacskip' environment variable.The naming convention is as follows:"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.Image Formats:==============U-Boot is capable of booting (and performing other auxiliary operations on)images in two formats:New uImage format (FIT)-----------------------Flexible and powerful format based on Flattened Image Tree -- FIT (similarto Flattened Device Tree). It allows the use of images with multiplecomponents (several kernels, ramdisks, etc.), with contents protected bySHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.Old uImage format-----------------Old image format is based on binary files which can be basically anything,preceded by a special header; see the definitions in include/image.h fordetails; basically, the header defines the following image properties:* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,  INTEGRITY).* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).* Compression Type (uncompressed, gzip, bzip2)* Load Address* Entry Point* Image Name* Image TimestampThe header is marked by a special Magic Number, and both the headerand the data portions of the image are secured against corruption byCRC32 checksums.Linux Support:==============Although U-Boot should support any OS or standalone applicationeasily, the main focus has always been on Linux during the design ofU-Boot.U-Boot includes many features that so far have been part of somespecial "boot loader" code within the Linux kernel. Also, any"initrd" images to be used are no longer part of one big Linux image;instead, kernel and "initrd" are separate images. This implementationserves several purposes:- the same features can be used for other OS or standalone  applications (for instance: using compressed images to reduce the  Flash memory footprint)- it becomes much easier to port new Linux kernel versions because  lots of low-level, hardware dependent stuff are done by U-Boot- the same Linux kernel image can now be used with different "initrd"  images; of course this also means that different kernel images can  be run with the same "initrd". This makes testing easier (you don't  have to build a new "zImage.initrd" Linux image when you just  change a file in your "initrd"). Also, a field-upgrade of the  software is easier now.Linux HOWTO:============Porting Linux to U-Boot based systems:---------------------------------------U-Boot cannot save you from doing all the necessary modifications toconfigure the Linux device drivers for use with your target hardware(no, we don't intend to provide a full virtual machine interface toLinux :-).But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).Just make sure your machine specific header file (for instanceinclude/asm-ppc/tqm8xx.h) includes the same definition of the BoardInformation structure as we define in include/asm-<arch>/u-boot.h,and make sure that your definition of IMAP_ADDR uses the same valueas your U-Boot configuration in CONFIG_SYS_IMMR.Note that U-Boot now has a driver model, a unified model for drivers.If you are adding a new driver, plumb it into driver model. If thereis no uclass available, you are encouraged to create one. Seedoc/driver-model.Configuring the Linux kernel:-----------------------------No specific requirements for U-Boot. Make sure you have some rootdevice (initial ramdisk, NFS) for your target system.Building a Linux Image:-----------------------With U-Boot, "normal" build targets like "zImage" or "bzImage" arenot used. If you use recent kernel source, a new build target"uImage" will exist which automatically builds an image usable byU-Boot. Most older kernels also have support for a "pImage" target,which was introduced for our predecessor project PPCBoot and uses a100% compatible format.Example:make TQM850L_defconfigmake oldconfigmake depmake uImageThe "uImage" build target uses a special tool (in 'tools/mkimage') toencapsulate a compressed Linux kernel image with header information,CRC32 checksum etc. for use with U-Boot. This is what we are doing:* build a standard "vmlinux" kernel image (in ELF binary format):* convert the kernel into a raw binary image:${CROSS_COMPILE}-objcopy -O binary \ -R .note -R .comment \ -S vmlinux linux.bin* compress the binary image:gzip -9 linux.bin* package compressed binary image for U-Boot:mkimage -A ppc -O linux -T kernel -C gzip \-a 0 -e 0 -n "Linux Kernel Image" \-d linux.bin.gz uImageThe "mkimage" tool can also be used to create ramdisk images for usewith U-Boot, either separated from the Linux kernel image, orcombined into one file. "mkimage" encapsulates the images with a 64byte header containing information about target architecture,operating system, image type, compression method, entry points, timestamp, CRC32 checksums, etc."mkimage" can be called in two ways: to verify existing images andprint the header information, or to build new images.In the first form (with "-l" option) mkimage lists the informationcontained in the header of an existing U-Boot image; this includeschecksum verification:tools/mkimage -l image  -l ==> list image header informationThe second form (with "-d" option) is used to build a U-Boot imagefrom a "data file" which is used as image payload:tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \      -n name -d data_file image  -A ==> set architecture to 'arch'  -O ==> set operating system to 'os'  -T ==> set image type to 'type'  -C ==> set compression type 'comp'  -a ==> set load address to 'addr' (hex)  -e ==> set entry point to 'ep' (hex)  -n ==> set image name to 'name'  -d ==> use image data from 'datafile'Right now, all Linux kernels for PowerPC systems use the same loadaddress (0x00000000), but the entry point address depends on thekernel version:- 2.2.x kernels have the entry point at 0x0000000C,- 2.3.x and later kernels have the entry point at 0x00000000.So a typical call to build a U-Boot image would read:-> tools/mkimage -n '2.4.4 kernel for TQM850L' \> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \> examples/uImage.TQM850LImage Name:   2.4.4 kernel for TQM850LCreated:      Wed Jul 19 02:34:59 2000Image Type:   PowerPC Linux Kernel Image (gzip compressed)Data Size:    335725 Bytes = 327.86 kB = 0.32 MBLoad Address: 0x00000000Entry Point:  0x00000000To verify the contents of the image (or check for corruption):-> tools/mkimage -l examples/uImage.TQM850LImage Name:   2.4.4 kernel for TQM850LCreated:      Wed Jul 19 02:34:59 2000Image Type:   PowerPC Linux Kernel Image (gzip compressed)Data Size:    335725 Bytes = 327.86 kB = 0.32 MBLoad Address: 0x00000000Entry Point:  0x00000000NOTE: for embedded systems where boot time is critical you can tradespeed for memory and install an UNCOMPRESSED image instead: thisneeds more space in Flash, but boots much faster since it does notneed to be uncompressed:-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz-> tools/mkimage -n '2.4.4 kernel for TQM850L' \> -A ppc -O linux -T kernel -C none -a 0 -e 0 \> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \> examples/uImage.TQM850L-uncompressedImage Name:   2.4.4 kernel for TQM850LCreated:      Wed Jul 19 02:34:59 2000Image Type:   PowerPC Linux Kernel Image (uncompressed)Data Size:    792160 Bytes = 773.59 kB = 0.76 MBLoad Address: 0x00000000Entry Point:  0x00000000Similar you can build U-Boot images from a 'ramdisk.image.gz' filewhen your kernel is intended to use an initial ramdisk:-> tools/mkimage -n 'Simple Ramdisk Image' \> -A ppc -O linux -T ramdisk -C gzip \> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrdImage Name:   Simple Ramdisk ImageCreated:      Wed Jan 12 14:01:50 2000Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)Data Size:    566530 Bytes = 553.25 kB = 0.54 MBLoad Address: 0x00000000Entry Point:  0x00000000The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"option performs the converse operation of the mkimage's second form (the "-d"option). Given an image built by mkimage, the dumpimage extracts a "data file"from the image:tools/dumpimage -i image -T type -p position data_file  -i ==> extract from the 'image' a specific 'data_file'  -T ==> set image type to 'type'  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'Installing a Linux Image:-------------------------To downloading a U-Boot image over the serial (console) interface,you must convert the image to S-Record format:objcopy -I binary -O srec examples/image examples/image.srecThe 'objcopy' does not understand the information in the U-Bootimage header, so the resulting S-Record file will be relative toaddress 0x00000000. To load it to a given address, you need tospecify the target address as 'offset' parameter with the 'loads'command.Example: install the image to address 0x40100000 (which on theTQM8xxL is in the first Flash bank):=> erase 40100000 401FFFFF.......... doneErased 8 sectors=> loads 40100000## Ready for S-Record download ...~>examples/image.srec1 2 3 4 5 6 7 8 9 10 11 12 13 ......15989 15990 15991 15992[file transfer complete][connected]## Start Addr = 0x00000000You can check the success of the download using the 'iminfo' command;this includes a checksum verification so you can be sure no datacorruption happened:=> imi 40100000## Checking Image at 40100000 ...   Image Name: 2.2.13 for initrd on TQM850L   Image Type: PowerPC Linux Kernel Image (gzip compressed)   Data Size: 335725 Bytes = 327 kB = 0 MB   Load Address: 00000000   Entry Point: 0000000c   Verifying Checksum ... OKBoot Linux:-----------The "bootm" command is used to boot an application that is stored inmemory (RAM or Flash). In case of a Linux kernel image, the contentsof the "bootargs" environment variable is passed to the kernel asparameters. You can check and modify this variable using the"printenv" and "setenv" commands:=> printenv bootargsbootargs=root=/dev/ram=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2=> printenv bootargsbootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2=> bootm 40020000## Booting Linux kernel at 40020000 ...   Image Name: 2.2.13 for NFS on TQM850L   Image Type: PowerPC Linux Kernel Image (gzip compressed)   Data Size: 381681 Bytes = 372 kB = 0 MB   Load Address: 00000000   Entry Point: 0000000c   Verifying Checksum ... OK   Uncompressing Kernel Image ... OKLinux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:35:17 MEST 2000Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2time_init: decrementer frequency = 187500000/60Calibrating delay loop... 49.77 BogoMIPSMemory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]...If you want to boot a Linux kernel with initial RAM disk, you passthe memory addresses of both the kernel and the initrd image (PPBCOOTformat!) to the "bootm" command:=> imi 40100000 40200000## Checking Image at 40100000 ...   Image Name: 2.2.13 for initrd on TQM850L   Image Type: PowerPC Linux Kernel Image (gzip compressed)   Data Size: 335725 Bytes = 327 kB = 0 MB   Load Address: 00000000   Entry Point: 0000000c   Verifying Checksum ... OK## Checking Image at 40200000 ...   Image Name: Simple Ramdisk Image   Image Type: PowerPC Linux RAMDisk Image (gzip compressed)   Data Size: 566530 Bytes = 553 kB = 0 MB   Load Address: 00000000   Entry Point: 00000000   Verifying Checksum ... OK=> bootm 40100000 40200000## Booting Linux kernel at 40100000 ...   Image Name: 2.2.13 for initrd on TQM850L   Image Type: PowerPC Linux Kernel Image (gzip compressed)   Data Size: 335725 Bytes = 327 kB = 0 MB   Load Address: 00000000   Entry Point: 0000000c   Verifying Checksum ... OK   Uncompressing Kernel Image ... OK## Loading RAMDisk Image at 40200000 ...   Image Name: Simple Ramdisk Image   Image Type: PowerPC Linux RAMDisk Image (gzip compressed)   Data Size: 566530 Bytes = 553 kB = 0 MB   Load Address: 00000000   Entry Point: 00000000   Verifying Checksum ... OK   Loading Ramdisk ... OKLinux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:32:08 MEST 2000Boot arguments: root=/dev/ramtime_init: decrementer frequency = 187500000/60Calibrating delay loop... 49.77 BogoMIPS...RAMDISK: Compressed image found at block 0VFS: Mounted root (ext2 filesystem).bash#Boot Linux and pass a flat device tree:-----------First, U-Boot must be compiled with the appropriate defines. See the sectiontitled "Linux Kernel Interface" above for a more in depth explanation. Thefollowing is an example of how to start a kernel and pass an updatedflat device tree:=> print oftaddroftaddr=0x300000=> print oftoft=oftrees/mpc8540ads.dtb=> tftp $oftaddr $oftSpeed: 1000, full duplexUsing TSEC0 deviceTFTP from server 192.168.1.1; our IP address is 192.168.1.101Filename 'oftrees/mpc8540ads.dtb'.Load address: 0x300000Loading: #doneBytes transferred = 4106 (100a hex)=> tftp $loadaddr $bootfileSpeed: 1000, full duplexUsing TSEC0 deviceTFTP from server 192.168.1.1; our IP address is 192.168.1.2Filename 'uImage'.Load address: 0x200000Loading:############doneBytes transferred = 1029407 (fb51f hex)=> print loadaddrloadaddr=200000=> print oftaddroftaddr=0x300000=> bootm $loadaddr - $oftaddr## Booting image at 00200000 ...   Image Name: Linux-2.6.17-dirty   Image Type: PowerPC Linux Kernel Image (gzip compressed)   Data Size: 1029343 Bytes = 1005.2 kB   Load Address: 00000000   Entry Point: 00000000   Verifying Checksum ... OK   Uncompressing Kernel Image ... OKBooting using flat device tree at 0x300000Using MPC85xx ADS machine descriptionMemory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb[snip]More About U-Boot Image Types:------------------------------U-Boot supports the following image types:   "Standalone Programs" are directly runnable in the environmentprovided by U-Boot; it is expected that (if they behavewell) you can continue to work in U-Boot after return fromthe Standalone Program.   "OS Kernel Images" are usually images of some Embedded OS whichwill take over control completely. Usually these programswill install their own set of exception handlers, devicedrivers, set up the MMU, etc. - this means, that you cannotexpect to re-enter U-Boot except by resetting the CPU.   "RAMDisk Images" are more or less just data blocks, and theirparameters (address, size) are passed to an OS kernel that isbeing started.   "Multi-File Images" contain several images, typically an OS(Linux) kernel image and one or more data images likeRAMDisks. This construct is useful for instance when you wantto boot over the network using BOOTP etc., where the bootserver provides just a single image file, but you want to getfor instance an OS kernel and a RAMDisk image."Multi-File Images" start with a list of image sizes, eachimage size (in bytes) specified by an "uint32_t" in networkbyte order. This list is terminated by an "(uint32_t)0".Immediately after the terminating 0 follow the images, one byone, all aligned on "uint32_t" boundaries (size rounded up toa multiple of 4 bytes).   "Firmware Images" are binary images containing firmware (likeU-Boot or FPGA images) which usually will be programmed toflash memory.   "Script files" are command sequences that will be executed byU-Boot's command interpreter; this feature is especiallyuseful when you configure U-Boot to use a real shell (hush)as command interpreter.Booting the Linux zImage:-------------------------On some platforms, it's possible to boot Linux zImage. This is doneusing the "bootz" command. The syntax of "bootz" command is the sameas the syntax of "bootm" command.Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supplykernel with raw initrd images. The syntax is slightly different, theaddress of the initrd must be augmented by it's size, in the followingformat: "<initrd addres>:<initrd size>".Standalone HOWTO:=================One of the features of U-Boot is that you can dynamically load andrun "standalone" applications, which can use some resources ofU-Boot like console I/O functions or interrupt services.Two simple examples are included with the sources:"Hello World" Demo:-------------------'examples/hello_world.c' contains a small "Hello World" Demoapplication; it is automatically compiled when you build U-Boot.It's configured to run at address 0x00040004, so you can play with itlike that:=> loads## Ready for S-Record download ...~>examples/hello_world.srec1 2 3 4 5 6 7 8 9 10 11 ...[file transfer complete][connected]## Start Addr = 0x00040004=> go 40004 Hello World! This is a test.## Starting application at 0x00040004 ...Hello Worldargc = 7argv[0] = "40004"argv[1] = "Hello"argv[2] = "World!"argv[3] = "This"argv[4] = "is"argv[5] = "a"argv[6] = "test."argv[7] = "<NULL>"Hit any key to exit ...## Application terminated, rc = 0x0Another example, which demonstrates how to register a CPM interrupthandler with the U-Boot code, can be found in 'examples/timer.c'.Here, a CPM timer is set up to generate an interrupt every second.The interrupt service routine is trivial, just printing a '.'character, but this is just a demo program. The application can becontrolled by the following keys:? - print current values og the CPM Timer registersb - enable interrupts and start timere - stop timer and disable interruptsq - quit application=> loads## Ready for S-Record download ...~>examples/timer.srec1 2 3 4 5 6 7 8 9 10 11 ...[file transfer complete][connected]## Start Addr = 0x00040004=> go 40004## Starting application at 0x00040004 ...TIMERS=0xfff00980Using timer 1  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0Hit 'b':[q, b, e, ?] Set interval 1000000 usEnabling timerHit '?':[q, b, e, ?] ........tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0Hit '?':[q, b, e, ?] .tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0Hit '?':[q, b, e, ?] .tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0Hit '?':[q, b, e, ?] .tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0Hit 'e':[q, b, e, ?] ...Stopping timerHit 'q':[q, b, e, ?] ## Application terminated, rc = 0x0Minicom warning:================Over time, many people have reported problems when trying to use the"minicom" terminal emulation program for serial download. I (wd)consider minicom to be broken, and recommend not to use it. UnderUnix, I recommend to use C-Kermit for general purpose use (andespecially for kermit binary protocol download ("loadb" command), anduse "cu" for S-Record download ("loads" command).  Seehttp://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.for help with kermit.Nevertheless, if you absolutely want to use it try adding thisconfiguration to your "File transfer protocols" section:   Name   ProgramName U/D FullScr IO-Red. MultiX  kermit  /usr/bin/kermit -i -l %l -s Y    U   Y   N  NY  kermit  /usr/bin/kermit -i -l %l -r N    D   Y   N  NNetBSD Notes:=============Starting at version 0.9.2, U-Boot supports NetBSD both as host(build U-Boot) and target system (boots NetBSD/mpc8xx).Building requires a cross environment; it is known to work onNetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will alsoneed gmake since the Makefiles are not compatible with BSD make).Note that the cross-powerpc package does not install include files;attempting to build U-Boot will fail because <machine/ansi.h> ismissing.  This file has to be installed and patched manually:# cd /usr/pkg/cross/powerpc-netbsd/include# mkdir powerpc# ln -s powerpc machine# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h# ${EDIT} powerpc/ansi.h## must remove __va_list, _BSD_VA_LISTNative builds *don't* work due to incompatibilities between nativeand U-Boot include files.Booting assumes that (the first part of) the image booted is astage-2 loader which in turn loads and then invokes the kernelproper. Loader sources will eventually appear in the NetBSD sourcetree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in themeantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gzImplementation Internals:=========================The following is not intended to be a complete description of everyimplementation detail. However, it should help to understand theinner workings of U-Boot and make it easier to port it to customhardware.Initial Stack, Global Data:---------------------------The implementation of U-Boot is complicated by the fact that U-Bootstarts running out of ROM (flash memory), usually without access tosystem RAM (because the memory controller is not initialized yet).This means that we don't have writable Data or BSS segments, and BSSis not initialized as zero. To be able to get a C environment workingat all, we have to allocate at least a minimal stack. Implementationoptions for this are defined and restricted by the CPU used: Some CPUmodels provide on-chip memory (like the IMMR area on MPC8xx andMPC826x processors), on others (parts of) the data cache can belocked as (mis-) used as memory, etc.Chris Hallinan posted a good summary of these issues to theU-Boot mailing list:Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?From: "Chris Hallinan" <clh@net1plus.com>Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)...Correct me if I'm wrong, folks, but the way I understand itis this: Using DCACHE as initial RAM for Stack, etc, does notrequire any physical RAM backing up the cache. The clevernessis that the cache is being used as a temporary supply ofnecessary storage before the SDRAM controller is setup. It'sbeyond the scope of this list to explain the details, but youcan see how this works by studying the cache architecture andoperation in the architecture and processor-specific manuals.OCM is On Chip Memory, which I believe the 405GP has 4K. Itis another option for the system designer to use as aninitial stack/RAM area prior to SDRAM being available. Eitheroption should work for you. Using CS 4 should be fine if yourboard designers haven't used it for something that wouldcause you grief during the initial boot! It is frequently notused.CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interferewith your processor/board/system design. The default valueyou will find in any recent u-boot distribution inwalnut.h should work for you. I'd set it to a value largerthan your SDRAM module. If you have a 64MB SDRAM module, setit above 400_0000. Just make sure your board has no resourcesthat are supposed to respond to that address! That code instart.S has been around a while and should work as is whenyou get the config right.-Chris HallinanDS4.COM, Inc.It is essential to remember this, since it has some impact on the Ccode for the initialization procedures:* Initialized global data (data segment) is read-only. Do not attempt  to write it.* Do not use any uninitialized global data (or implicitly initialized  as zero data - BSS segment) at all - this is undefined, initiali-  zation is performed later (when relocating to RAM).* Stack space is very limited. Avoid big data buffers or things like  that.Having only the stack as writable memory limits means we cannot usenormal global data to share information between the code. But itturned out that the implementation of U-Boot can be greatlysimplified by making a global data structure (gd_t) available to allfunctions. We could pass a pointer to this data as argument to _all_functions, but this would bloat the code. Instead we use a feature ofthe GCC compiler (Global Register Variables) to share the data: weplace a pointer (gd) to the global data into a register which wereserve for this purpose.When choosing a register for such a purpose we are restricted by therelevant  (E)ABI  specifications for the current architecture, and byGCC's implementation.For PowerPC, the following registers have specific use:R1:stack pointerR2:reserved for system useR3-R4:parameter passing and return valuesR5-R10: parameter passingR13:small data area pointerR30:GOT pointerR31:frame pointer(U-Boot also uses R12 as internal GOT pointer. r12is a volatile register so r12 needs to be reset whengoing back and forth between asm and C)    ==> U-Boot will use R2 to hold a pointer to the global data    Note: on PPC, we could use a static initializer (since the    address of the global data structure is known at compile time),    but it turned out that reserving a register results in somewhat    smaller code - although the code savings are not that big (on    average for all boards 752 bytes for the whole U-Boot image,    624 text + 127 data).On Blackfin, the normal C ABI (except for P3) is followed as documented here:http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface    ==> U-Boot will use P3 to hold a pointer to the global dataOn ARM, the following registers are used:R0:function argument word/integer resultR1-R3:function argument wordR9:platform specificR10:stack limit (used only if stack checking is enabled)R11:argument (frame) pointerR12:temporary workspaceR13:stack pointerR14:link registerR15:program counter    ==> U-Boot will use R9 to hold a pointer to the global data    Note: on ARM, only R_ARM_RELATIVE relocations are supported.On Nios II, the ABI is documented here:http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf    ==> U-Boot will use gp to hold a pointer to the global data    Note: on Nios II, we give "-G0" option to gcc and don't use gp    to access small data sections, so gp is free.On NDS32, the following registers are used:R0-R1:argument/returnR2-R5:argumentR15:temporary register for assemblerR16:trampoline registerR28:frame pointer (FP)R29:global pointer (GP)R30:link register (LP)R31:stack pointer (SP)PC:program counter (PC)    ==> U-Boot will use R10 to hold a pointer to the global dataNOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,or current versions of GCC may "optimize" the code too much.Memory Management:------------------U-Boot runs in system state and uses physical addresses, i.e. theMMU is not used either for address mapping nor for memory protection.The available memory is mapped to fixed addresses using the memorycontroller. In this process, a contiguous block is formed for eachmemory type (Flash, SDRAM, SRAM), even when it consists of severalphysical memory banks.U-Boot is installed in the first 128 kB of the first Flash bank (onTQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). Afterbooting and sizing and initializing DRAM, the code relocates itselfto the upper end of DRAM. Immediately below the U-Boot code somememory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LENconfiguration setting]. Below that, a structure with global BoardInfo data is placed, followed by the stack (growing downward).Additionally, some exception handler code is copied to the low 8 kBof DRAM (0x00000000 ... 0x00001FFF).So a typical memory configuration with 16 MB of DRAM could look likethis:0x0000 0000Exception Vector code      :0x0000 1FFF0x0000 2000Free for Application Use      :      :      :      :0x00FB FF20Monitor Stack (Growing downward)0x00FB FFACBoard Info Data and permanent copy of global data0x00FC 0000Malloc Arena      :0x00FD FFFF0x00FE 0000RAM Copy of Monitor Code...eventually: LCD or video framebuffer...eventually: pRAM (Protected RAM - unchanged by reset)0x00FF FFFF[End of RAM]System Initialization:----------------------In the reset configuration, U-Boot starts at the reset entry point(on most PowerPC systems at address 0x00000100). Because of the resetconfiguration for CS0# this is a mirror of the on board Flash memory.To be able to re-map memory U-Boot then jumps to its link address.To be able to implement the initialization code in C, a (small!)initial stack is set up in the internal Dual Ported RAM (in case CPUswhich provide such a feature like MPC8xx or MPC8260), or in a lockedpart of the data cache. After that, U-Boot initializes the CPU core,the caches and the SIU.Next, all (potentially) available memory banks are mapped using apreliminary mapping. For example, we put them on 512 MB boundaries(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flashon 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A isprogrammed for SDRAM access. Using the temporary configuration, asimple memory test is run that determines the size of the SDRAMbanks.When there is more than one SDRAM bank, and the banks are ofdifferent size, the largest is mapped first. For equal size, the firstbank (CS2#) is mapped first. The first mapping is always for address0x00000000, with any additional banks following immediately to createcontiguous memory starting from 0.Then, the monitor installs itself at the upper end of the SDRAM areaand allocates memory for use by malloc() and for the global BoardInfo data; also, the exception vector code is copied to the low RAMpages, and the final stack is set up.Only after this relocation will you have a "normal" C environment;until that you are restricted in several ways, mostly because you arerunning from ROM, and because the code will have to be relocated to anew address in RAM.U-Boot Porting Guide:----------------------[Based on messages by Jerry Van Baren in the U-Boot-Users mailinglist, October 2002]int main(int argc, char *argv[]){sighandler_t no_more_time;signal(SIGALRM, no_more_time);alarm(PROJECT_DEADLINE - toSec (3 * WEEK));if (available_money > available_manpower) {Pay consultant to port U-Boot;return 0;}Download latest U-Boot source;Subscribe to u-boot mailing list;if (clueless)email("Hi, I am new to U-Boot, how do I get started?");while (learning) {Read the README file in the top level directory;Readhttp://www.denx.de/twiki/bin/view/DULG/Manual;Read applicable doc/*.README;Read the source, Luke;/* find . -name "*.[chS]" | xargs grep -i <keyword> */}if (available_money > toLocalCurrency ($2500))Buy a BDI3000;elseAdd a lot of aggravation and time;if (a similar board exists) {/* hopefully... */cp -a board/<similar> board/<myboard>cp include/configs/<similar>.h include/configs/<myboard>.h} else {Create your own board support subdirectory;Create your own board include/configs/<myboard>.h file;}Edit new board/<myboard> filesEdit new include/configs/<myboard>.hwhile (!accepted) {while (!running) {do {Add / modify source code;} until (compiles);Debug;if (clueless)email("Hi, I am having problems...");}Send patch file to the U-Boot email list;if (reasonable critiques)Incorporate improvements from email list code review;elseDefend code as written;}return 0;}void no_more_time (int sig){      hire_a_guru();}Coding Standards:-----------------All contributions to U-Boot should conform to the Linux kernelcoding style; see the file "Documentation/CodingStyle" and the script"scripts/Lindent" in your Linux kernel source directory.Source files originating from a different project (for example theMTD subsystem) are generally exempt from these guidelines and are notreformatted to ease subsequent migration to newer versions of thosesources.Please note that U-Boot is implemented in C (and to some small parts inAssembler); no C++ is used, so please do not use C++ style comments (//)in your code.Please also stick to the following formatting rules:- remove any trailing white space- use TAB characters for indentation and vertical alignment, not spaces- make sure NOT to use DOS '\r\n' line feeds- do not add more than 2 consecutive empty lines to source files- do not add trailing empty lines to source filesSubmissions which do not conform to the standards may be returnedwith a request to reformat the changes.Submitting Patches:-------------------Since the number of patches for U-Boot is growing, we need toestablish some rules. Submissions which do not conform to these rulesmay be rejected, even when they contain important and valuable stuff.Please seehttp://www.denx.de/wiki/U-Boot/Patches for details.Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;seehttp://lists.denx.de/mailman/listinfo/u-bootWhen you send a patch, please include the following information withit:* For bug fixes: a description of the bug and how your patch fixes  this bug. Please try to include a way of demonstrating that the  patch actually fixes something.* For new features: a description of the feature and your  implementation.* A CHANGELOG entry as plaintext (separate from the patch)* For major contributions, your entry to the CREDITS file* When you add support for a new board, don't forget to add a  maintainer e-mail address to the boards.cfg file, too.* If your patch adds new configuration options, don't forget to  document these in the README file.* The patch itself. If you are using git (which is *strongly*  recommended) you can easily generate the patch using the  "git format-patch". If you then use "git send-email" to send it to  the U-Boot mailing list, you will avoid most of the common problems  with some other mail clients.  If you cannot use git, use "diff -purN OLD NEW". If your version of  diff does not support these options, then get the latest version of  GNU diff.  The current directory when running this command shall be the parent  directory of the U-Boot source tree (i. e. please make sure that  your patch includes sufficient directory information for the  affected files).  We prefer patches as plain text. MIME attachments are discouraged,  and compressed attachments must not be used.* If one logical set of modifications affects or creates several  files, all these changes shall be submitted in a SINGLE patch file.* Changesets that contain different, unrelated modifications shall be  submitted as SEPARATE patches, one patch per changeset.Notes:* Before sending the patch, run the MAKEALL script on your patched  source tree and make sure that no errors or warnings are reported  for any of the boards.* Keep your modifications to the necessary minimum: A patch  containing several unrelated changes or arbitrary reformats will be  returned with a request to re-formatting / split it.* If you modify existing code, make sure that your new code does not  add to the memory footprint of the code ;-) Small is beautiful!  When adding new features, these should compile conditionally only  (using #ifdef), and the resulting code with the new feature  disabled must not need more memory than the old code without your  modification.* Remember that there is a size limit of 100 kB per message on the  u-boot mailing list. Bigger patches will be moderated. If they are  reasonable and not too big, they will be acknowledged. But patches  bigger than the size limit should be avoided.