AMD P-State EPP Won't Be Ready Until Linux 6.3

Written by Michael Larabel in AMD on 12 December 2022 at 07:00 AM EST. 8 Comments
For those that were holding out hope that the AMD P-State Linux driver's EPP functionality for more power/performance control under Linux would be ready for the Linux 6.2 kernel merge window, it's been rejected for the cycle and will be held off until at least the Linux 6.3 cycle begins in February.

AMD P-State EPP is a big improvement with this Energy Performance Preference (EPP) mode over the existing passive amd_pstate mode currently found within the mainline Linux kernel. With AMD P-State EPP on some systems where the P-State driver currently yields lower performance than using the generic ACPI CPUFreq driver, P-State EPP aims to close that gap. As another step ahead AMD also recently posted P-State Guided Autonomous Mode as another power/performance improvement for Ryzen and EPYC systems on Linux.

For those that were hoping P-State EPP would at least be ready for the Linux 6.2 merge window that's now happening, the code has been deemed not ready by Rafael Wysocki of Intel who serves as the Linux kernel's ACPI and power management maintainer. He wrote on the kernel mailing list:
I honestly don't think that this work is ready for 6.2.

The number of patches in the series seems to change frequently and there are active discussions around specific patches.

Accordingly, I will not consider applying it until 6.2-rc1 is out.

To which AMD engineers are now going to revise the patch series with some additional fixes and documentation to the AMD P-State EPP mode. It's too bad it has taken so long for this AMD P-State code to mature with the AMD P-State driver supporting processors back to the Zen 2 series where ACPI CPPC support was first introduced.

Here's to hoping that both AMD P-State EPP and the Guided Autonomous Mode functionality will be ready for mainlining come the Linux 6.3 cycle for enhancing AMD Ryzen/EPYC power/performance under Linux.
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