AMD Posts P-State EPP v9 Driver That Aims To Be Ready For Linux 6.3

Written by Michael Larabel in AMD on 26 December 2022 at 07:05 AM EST. 5 Comments
While the Linux 6.2 kernel merge window just wrapped up, AMD's P-State EPP driver was deemed not ready for making it this cycle. However, with AMD having now iterated it to a ninth revision, it's looking like this P-State "Energy Performance Preference" functionality over the existing P-State driver support will be ready for merging come Linux 6.3.

AMD Linux engineer Perry Yuan has posted a ninth set of the P-State EPP driver patches that aim for better performance and power control over the existing and mainlined AMD P-State driver. This functionality builds off the ACPI CPPC Energy Preference Performance (EPP) knob.
"AMD Energy Performance Preference (EPP) provides a hint to the hardware if software wants to bias toward performance (0x0) or energy efficiency (0xff) The lowlevel power firmware will calculate the runtime frequency according to the EPP preference value. So the EPP hint will impact the CPU cores frequency responsiveness."

Separately, AMD Linux engineers have also been working on a Guided Autonomous Mode for P-State too.

With today's v9 patches the code has been updated to address feedback raised by prior upstream code review, additional "reviewed-by" tags, and some other basic fixes. It looks though like things are finally settling down for the AMD P-State EPP code for enhancing power/performance efficiency for modern Ryzen and EPYC processors.

Those interested in testing the latest AMD P-State EPP patches can find them on the kernel mailing list while hopefully we'll see them mainlined for Linux 6.3 to help improve the performance in some areas where currently using AMD P-State can fall short compared to the generic ACPI CPUFreq driver.
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