Linux 6.1-rc7 Makes It Easier To Manage The AMD P-State Driver

With the Linux 6.1-rc7 kernel set to be released later today, it will become easier making use of the AMD P-State driver for that enhanced CPU frequency scaling driver intended for Zen 2 and newer EPYC/Ryzen platforms that make use of ACPI CPPC.

Merged to mainline on Friday as part of the "fixes" for Linux 6.1-rc7 is the set of patches to make amd-pstate a built-in driver so that it can take precedence over acpi-cpufreq by default and to introduce the new options to disable that behavior if wanting to fallback to the generic ACPI CPUFreq driver instead.

These patches were talked about on Phoronix last week in New Patches Allow More Easily Managing The AMD P-State Linux Driver. Since then it's been decided to pick up this material for Linux 6.1 rather than wait for Linux 6.2. Besides making the amd_pstate driver a built-in, it adds the amd_pstate=disable option if wanting to not use this driver on a supported system and to instead use ACPI CPUFreq. There is also amd_pstate=passive if wanting to load the AMD P-State driver in its passive operation mode.

AMD isn't yet encouraging the amd_pstate driver to be used by default but the plan for that is to happen once AMD P-State EPP is ready and merged. The AMD P-State EPP code should resolve some known performance issues with the current amd_pstate code.

Long story short, thanks to the merged power management fixes, amd_pstate is now a built-in driver and there are the new convenient kernel options for disabling its behavior or starting in passive mode. There is also a fix as part of that pull request to fix amd_pstate initialization after running the kernel via Kexec.