20.1.HSMP device¶

amd_hsmp driver under drivers/platforms/x86/amd/hsmp/ has separate driver filesfor ACPI object based probing, platform device based probing and for the commoncode for these two drivers.

Kconfig option CONFIG_AMD_HSMP_PLAT compiles plat.c and creates amd_hsmp.ko.Kconfig option CONFIG_AMD_HSMP_ACPI compiles acpi.c and creates hsmp_acpi.ko.Selecting any of these two configs automatically selects CONFIG_AMD_HSMP. Thiscompiles common code hsmp.c and creates hsmp_common.ko module.

Both the ACPI and plat drivers create the miscdevice /dev/hsmp to letuser space programs run hsmp mailbox commands.

The ACPI object format supported by the driver is defined below.

$ ls -al /dev/hsmpcrw-r--r-- 1 root root 10, 123 Jan 21 21:41 /dev/hsmp

Characteristics of the dev node:

• Write mode is used for running set/configure commands

• Read mode is used for running get/status monitor commands

Access restrictions:

• Only root user is allowed to open the file in write mode.

• The file can be opened in read mode by all the users.

In-kernel integration:

• Other subsystems in the kernel can use the exported transportfunctionhsmp_send_message().

• Locking across callers is taken care by the driver.

20.2.HSMP sysfs interface¶

1. Metrics table binary sysfs

AMD MI300A MCM provides GET_METRICS_TABLE message to retrievemost of the system management information from SMU in one go.

The metrics table is made available as hexadecimal sysfs binary fileunder per socket sysfs directory created at/sys/devices/platform/amd_hsmp/socket%d/metrics_bin

Note:lseek() is not supported as entire metrics table is read.

Metrics table definitions will be documented as part of Public PPR.The same is defined in the amd_hsmp.h header.

2. HSMP telemetry sysfs files

Following sysfs files are available at /sys/devices/platform/AMDI0097:0X/.

• c0_residency_input: Percentage of cores in C0 state.

• prochot_status: Reports 1 if the processor is at thermal threshold value,0 otherwise.

• smu_fw_version: SMU firmware version.

• protocol_version: HSMP interface version.

• ddr_max_bw: Theoretical maximum DDR bandwidth in GB/s.

• ddr_utilised_bw_input: Current utilized DDR bandwidth in GB/s.

• ddr_utilised_bw_perc_input(%): Percentage of current utilized DDR bandwidth.

• mclk_input: Memory clock in MHz.

• fclk_input: Fabric clock in MHz.

• clk_fmax: Maximum frequency of socket in MHz.

• clk_fmin: Minimum frequency of socket in MHz.

• cclk_freq_limit_input: Core clock frequency limit per socket in MHz.

• pwr_current_active_freq_limit: Current active frequency limit of socketin MHz.

• pwr_current_active_freq_limit_source: Source of current active frequencylimit.

20.3.ACPI device object format¶

The ACPI object format expected from the amd_hsmp driverfor socket with ID00 is given below:

Device(HSMP)              {                      Name(_HID, "AMDI0097")                      Name(_UID, "ID00")                      Name(HSE0, 0x00000001)                      Name(RBF0, ResourceTemplate()                      {                              Memory32Fixed(ReadWrite, 0xxxxxxx, 0x00100000)                      })                      Method(_CRS, 0, NotSerialized)                      {                              Return(RBF0)                      }                      Method(_STA, 0, NotSerialized)                      {                              If(LEqual(HSE0, One))                              {                                      Return(0x0F)                              }                              Else                              {                                      Return(Zero)                              }                      }                      Name(_DSD, Package(2)                      {                              Buffer(0x10)                              {                                      0x9D, 0x61, 0x4D, 0xB7, 0x07, 0x57, 0xBD, 0x48,                                      0xA6, 0x9F, 0x4E, 0xA2, 0x87, 0x1F, 0xC2, 0xF6                              },                              Package(3)                              {                                      Package(2) {"MsgIdOffset", 0x00010934},                                      Package(2) {"MsgRspOffset", 0x00010980},                                      Package(2) {"MsgArgOffset", 0x000109E0}                              }                      })              }

20.4.HSMP HWMON interface¶

HSMP power sensors are registered with the hwmon interface. A separate hwmondirectory is created for each socket and the following files are generatedwithin the hwmon directory.- power1_input (read only)- power1_cap_max (read only)- power1_cap (read, write)

20.5.An example¶

To access hsmp device from a C program.First, you need to include the headers:

#include <linux/amd_hsmp.h>

Which defines the supported messages/message IDs.

Next thing, open the device file, as follows:

int file;file = open("/dev/hsmp", O_RDWR);if (file < 0) {  /* ERROR HANDLING; you can check errno to see what went wrong */  exit(1);}

The following IOCTL is defined:

ioctl(file,HSMP_IOCTL_CMD,structhsmp_message*msg)

The argument is a pointer to a:

struct hsmp_message {    __u32   msg_id;                         /* Message ID */    __u16   num_args;                       /* Number of input argument words in message */    __u16   response_sz;                    /* Number of expected output/response words */    __u32   args[HSMP_MAX_MSG_LEN];         /* argument/response buffer */    __u16   sock_ind;                       /* socket number */};

The ioctl would return a non-zero on failure; you can read errno to seewhat happened. The transaction returns 0 on success.

More details on the interface and message definitions can be found in chapter“7 Host System Management Port (HSMP)” of the respective family/model PPReg:https://docs.amd.com/v/u/en-US/55898_B1_pub_0_50

User space C-APIs are made available by linking against the esmi library,which is provided by the E-SMS projecthttps://www.amd.com/en/developer/e-sms.html.See:https://github.com/amd/esmi_ib_library