.. SPDX-License-Identifier: GPL-2.0
amd apml modules (apml_sbtsi and apml_sbrmi)
amd-apml: APML interface drivers for BMC
EPYC processors from AMD provide APML interface for BMC users to monitor and configure the system parameters via the Advanced Platform Management List (APML) interface defined in EPYC processor PPR.
This chapter defines custom protocols over i2c/i3c bus
- Mailbox
- CPUID [RO]
- MCA MSR {RO]
- RMI/TSI register [RW]
module_i2c_i3c based sbrmi and sbtsi modules, which are probed as i2c or i3c client devices, depending on the platforms DTS.
https://developer.amd.com/resources/epyc-resources/epyc-specifications
APMl library provides C API fo the user space application on top of this module.
Disclaimer
The amd apml modules are supported only on AMD Family 19h (including third-generation AMD EPYC processors (codenamed "Milan")) or later CPUs. Using the amd apml modules on earlier CPUs could produce unexpected results, and may cause the processor to operate outside of your motherboard or system specifications. Correspondingly, defaults to only executing on AMD Family 19h Model (0h ~ 1Fh & 30h ~ 3Fh) server line of processors.
Interface
Both apml_sbtsi and apml_sbrmi modules register a misc_device to provide ioctl interface to user space, allowing them to run these custom protocols.
apml_sbtsi module registers hwmon sensors for monitoring current temperature, managing max and min thresholds.
apml_sbrmi module registers hwmon sensors for monitoring power_cap_max, current power consumption and managing power_cap.
Build and Install
Kernel development packages for the running kernel need to be installed prior to building the amd apml modules. A Makefile is provided which should work with most kernel source trees.
To cross compile for arm based BMC
export CC=arm-openbmc-linux-gnueabi-gcc # Or similar export ARCH=arm KDIR=
To build the kernel module:
#> make
To install the kernel module:
#> sudo make modules_install
To clean the kernel module build directory:
#> make clean
Loading
If the apml modules were installed you should use the modprobe command to load the module.
#> sudo modprobe apml_sbrmi apml_sbtsi
The apml modules can also be loaded using insmod if the module was not installed:
#> sudo insmod ./apml_sbrmi.ko #> sudo insmod ./apml_sbtsi.ko