a

Create a default configuration file:

The default configuration file allows theautotools programs to generate a.config file that defines the featuresmake will build into the image.

Loading U-Boot (boot.bin)

Below are three examples for the SAM9X60 that will load U-Boot (boot.bin) from external NVM memory to internal SRAM.

The first example will load U-Boot from SD Memory Card:

1   CONFIG_SAM9X60_<board>=y2   CONFIG_RAM_256MB=y3   CONFIG_SDCARD=y4   CONFIG_DEBUG=y5   CONFIG_THUMB=y

Line 1: Defines the board name. Used in the mainmakefile. Also used as a macro for board-specific initialization.
Line 2: Memory size of external RAM.
Line 3: Boots from SD Memory Card.
Line 4: Enables debug/log messages to be displayed on the console.
Line 5: Supports thumb instruction set. This is set only for ARM9 devices and not for Arm^® Cortex^® A5, which supports Thumb-2 instructions.

The second example will load U-Boot from NAND Flash memory:

1   CONFIG_SAM9X60_<board>=y2   CONFIG_RAM_256MB=y3   CONFIG_NANDFLASH=y4   # CONFIG_PMECC_AUTO_DETECT is not set5   CONFIG_PMECC_CORRECT_BITS_8=y6   CONFIG_IMG_SIZE="0x000c0000"7   CONFIG_DEBUG=y8   CONFIG_THUMB=y

Line 1: Defines the board name. Used in the mainmakefile. Also used as a macro for board-specific initialization.
Line 2: Memory size of external RAM.
Line 3: Boots from NAND Flash memory.
Line 4: For an ONFI compliant NAND, the ECC correction is automatically activated. Refer to the SAMA5D2 Series datasheet sections 16.4.7.1 and 16.4.7.2 or SAM9X60 datasheet sections 11.4.7.1 and 11.4.7.2.
Line 5: Specifies the PMECC error correction bits. Used whenCONFIG_PMECC_AUTO_DETECT is not set.
Line 6: Size of the U-Boot (boot.bin) image (in HEX) to be loaded byat91bootstrap.
Line 7: Enables debug/log messages to be displayed on the console.
Line 8: Supports thumb instruction set. This is set only for ARM9 devices and not for Cortex A5 which supports Thumb-2 instructions.

The third example will load U-Boot from QSPI Flash memory:

1   CONFIG_SAM9X60_<board>=y2   CONFIG_RAM_256MB=y3   CONFIG_SPI_CLK=500000004   CONFIG_IMG_ADDRESS="0x00040000"5   CONFIG_IMG_SIZE="0x000c0000"6   CONFIG_DEBUG=y

Line 1: Defines the board name. Used in the mainmakefile. Also used as a macro for board-specific initialization.
Line 2: Memory size of external RAM.
Line 3: SPI Clock frequency.
Line 4: Memory location in QSPI Flash memory where U-Boot (boot.bin) is stored. Theat91bootstrap copiesboot.bin from this address location to an address location specified in external RAM.
Line 5: Size of theboot.bin image (in HEX) to be loaded byat91bootstrap.
Line 6: Enables debug/log messages to be displayed on the console.

Loading Linux

Below are three examples for the SAM9X60 that will load a Linux image from external NVM memory to external RAM.

The first example will load Linux image from SD Memory Card:

1   CONFIG_SAM9X60_<board>=y2   CONFIG_RAM_256MB=y3   CONFIG_SDCARD=y4   CONFIG_LOAD_LINUX=y5   CONFIG_IMAGE_NAME="zImage"6   CONFIG_DEBUG=y7   CONFIG_THUMB=y

Line 1: Defines the board name. Used in the mainmakefile. Also used as a macro for board-specific initialization.
Line 2: Memory size of external RAM.
Line 3: Boots from SD Memory Card.
Line 4: Boots Linux directly.
Line 5: Name of the Linux image file.
Line 6: Enables debug/log messages to be displayed on the console.
Line 7: Supports thumb instruction set. This is set only for ARM9 devices and not for Cortex A5 which supports Thumb-2 instructions.

The second example will load Linux image from NAND Flash memory:

 1   CONFIG_SAM9X60_<board>=y 2   CONFIG_RAM_256MB=y 3   CONFIG_NANDFLASH=y 4   CONFIG_LOAD_LINUX=y 5   CONFIG_IMAGE_NAME="zImage" 6   # CONFIG_PMECC_AUTO_DETECT is not set 7   CONFIG_PMECC_CORRECT_BITS_8=y 8   CONFIG_IMG_SIZE="0x000c0000" 9   CONFIG_DEBUG=y10   CONFIG_THUMB=y

Line 1: Defines the board name. Used in the mainmakefile. Also used as a macro for board-specific initialization.
Line 2: Memory size of external RAM.
Line 3: Boots from NAND Flash memory.
Line 4: Boots Linux directly.
Line 5: Name of the Linux image file.
Line 6: For an ONFI compliant NAND, the ECC correction is automatically activated. Refer to the SAMA5D2 Series datasheet sections 16.4.7.1 and 16.4.7.2 or SAM9X60 datasheet sections 11.4.7.1 and 11.4.7.2.
Line 7: Specifies the PMECC error correction bits. Used whenCONFIG_PMECC_AUTO_DETECT is not set.
Line 8: Size of the Linux image (in HEX) to be loaded.
Line 9: Enables debug/log messages to be displayed on the console.
Line 10: Supports thumb instruction set. This is set only for ARM9 devices and not for Cortex A5 which supports Thumb-2 instructions.

The third example will load Linux image from QSPI Flash memory:

1   CONFIG_SAM9X60_<board>=y2   CONFIG_RAM_256MB=y3   CONFIG_SPI_CLK=500000004   CONFIG_OVERRIDE_CMDLINE=y5   CONFIG_IMG_ADDRESS="0x00200000"6   CONFIG_OF_OFFSET="0x00180000"7   CONFIG_LOAD_LINUX=y8   CONFIG_JUMP_ADDR="0x26F00000"9   CONFIG_DEBUG=y

Line 1: Defines the board name. Used in the main makefile. Also used as a macro for board-specific initialization.
Line 2: Memory size of external RAM.
Line 3: SPI Clock frequency.
Line 4: IfCONFIG_OVERRIDE_CMDLINE is selected, then you can override the kernel argument set byCONFIG_LINUX_KERNEL_ARG_STRING as shown in the figure below.

Line 5: Memory location in QSPI Flash memory where the Linux image is stored.
Line 6: Memory location in QSPI Flash memory where the Device Tree is stored.
Line 7: Boots Linux directly.
Line 8: The memory location in the external RAM where the Linux Image should be copied to.
Line 9: Enables debug/log messages to be displayed on the console.

Naming Convention

The suggested naming convention for your custom project default configuration is to concatenate the board name (<board>) with the NVM memory thatat91bootstrap will load from SD Memory Card, QSPI Flash, NAND Flash, etc. and the program that will be loaded, U-Boot, Linux, busybox, etc.

<board>_<nvm_boot_memory>_<uboot_or_linux>_defconfig

Legend:

• qspi – QSPI Flash Memory
• sd – SD Memory Card
  • if no number is given, boot from port 0
  • if number is given, boot from indicated port (for example, 1 = port 1)
• nf – NAND Flash Memory
• df – Serial/DataFlash Memory

Legend:

• uboot – Third-Stage Bootloader
• linux_image_dt – Linux kernel and Device Tree

b

Create a<board>.c file:

The<board>.c file performs all the hardware initialization of the custom project board.

Functionhw_init() is a mandatory function. It performs all of the peripheral and hardware initialization. Examine the<board>.c file that closely matches your custom project board design. In general, the following peripheral and hardware initializations must be performed:

• Clock initialization:
  • The PLLA is initialized and the MCK is switched to PLLA output.
  • Peripheral Clocks that are in use are initialized within the respective peripheral initialization routines.
• External DRAM initialization:
  • The most important function is external DRAM initialization (you will see them inside the#ifdef CONFIG_DDR2).
  • If you are using a similar SRAM from the evaluation kits, you can examine and reuse the DDR RAM configuration and initialization functions.
  • If a different DRAM is used, refer to the DRAM datasheet to gather information needed to alter the configuration and initialization functions.
  • Theddramc_init() function is implemented for external DRAM initialization called byhw_init(). Theddramc_init() calls theddramc_reg_config() function to populate the RAM configuration and timings followed by theddram_initialization.
• Pin initialization:
  • Pin initializations are initialized.
• External NVM initialization:
  • The external NVM that contains the third-stage bootloader or program to be loaded byat91bootstrap is initialized.
• Other initializations:
  • The bus matrix system, timer, debug console, LEDs, or anything specific to the custom project board is initialized.

c

Create a<board>.h file:

The<board>.h file provides definitions for the clock (Main and peripheral) and setting for all of the NVM memory on your custom project board.

Ensure the clock related to NVM memory settings are set to the values required. The clock settings depend on the choice for the clock source, i.e.:

• An external source of 8 to 24 MHz crystal oscillator
• External Clock Source
• Both external and internal clock 12 MHz RC
• Internal slow clock and 12 MHz RC

This will determine the clock definition forBOARD_MAINOSC.

Other required definitions are:

• Bus frequency
• Main clock frequency
• PLLA prescaler settings (multiplier and divider)
• Console UART baud

The NVM related definitions depend on what type of memory you choose.

For an SD Memory Card, the following definitions are required:

• CONFIG_SYS_BASE_SDHC: The address location where the peripheral is memory mapped.
• CONFIG_SYS_ID_SDHC: The peripheral ID.

For a NAND Flash memory, the following definitions are required:

• CONFIG_SYS_NAND_BASE: The address location where the External Bus Interface with NCS3 (chip select 3) is memory mapped.
• CONFIG_SYS_NAND_MASK_ALE: The Address Latch Enable line (A21 of the Static Memory Controller).
• CONFIG_SYS_NAND_MASK_CLE: The Command Latch Enable line (A22 of the Static Memory Controller).

• CONFIG_SYS_NAND_ENABLE_PIN: NAND Flash memory Chip Select pin
• CONFIG_SYS_NAND_OE_PIN: Output Enable pin
• CONFIG_SYS_NAND_WE_PIN: Write Enable pin
• CONFIG_SYS_NAND_ALE_PIN: Address Latch Enable pin (A21 of the Static Memory Controller)
• CONFIG_SYS_NAND_CLE_PIN: Command Latch Enable pin (A22 of the Static Memory Controller)

ForDataFlash Memory, the following definitions are required:

• CONFIG_SYS_SPI_CLOCK: SPI Clock Frequency (typically defined in thedefconfig file for the board)
• CONFIG_SYS_SPI_MODE: SPI mode
• CONFIG_SYS_BASE_SPI: The address location where the peripheral is memory mapped
• CONFIG_SYS_SPI_PCS: SPI Chip Select pin

d

Create aboard.mk file:

Edit theboard.mk file with the compiler and assembler flags.

e

Create aConfig.in.board file:

Edit theConfig.in.board file with the configuration choices used bymenuconfig.

f

If you are loading a Linux Image directly, create aConfig.in.linux_arg file:

If you wantat91bootstrap to load the Linux image directly, without loading a third-stage bootloader such as U-Boot, you will need to edit theConfig.in.linux_arg file with the boot arguments that will be passed to the Linux kernel.

You will also need to update theConfig.in.kernel file in theat91bootstrap root directory.

g

Create aConfig.in.boardname file:

This file definesCONFIG_BOARDNAME used by menuconfig to display the list of contributed boards a user can choose from. This file is sourced by thecontrib/board/Config.in.boardname which is in turn sourced byboard/Config.in, sourced by the mainConfig.in.

$ cd ~/project_1/at91bootstrap

$ make mrproper
$ make <board>_defconfig

What is the difference betweenmake clean andmake mrproper?

• make clean: Remove most generated files but keep the config and enough build support to build external modules
• make mrproper: Remove all generated files + config + various backup files

Anytime the configuration is changed, you should executemake mrproper.

$ make menuconfig

$ make

A working cross-toolchain for ARM-based MPU target is required to buildat91bootstrap.

Ensure you set theCROSS_COMPILE=<cross_compiler> andARCH=arm environment variables.

For example, if your cross-compiler executable isarm-linux-gcc thenCROSS_COMPILE=<path_to>/arm-linux-

$ cd ~/project_1/at91bootstrap/binaries