Linux 6.5 Now Defaults To AMD P-State "Active" EPP For Modern Ryzen Systems

The power management and ACPI feature changes have been merged for the in-development Linux 6.5 kernel. As usual, it's most interesting on the Intel and AMD fronts with the power management changes for this kernel that will be released as stable in August.

Most interesting with the power management updates this round are a set of AMD P-State driver fixes along with now defaulting to AMD P-State active (EPP) mode for modern systems. The AMD P-State driver is now used by default rather than CPUFreq for Zen 2 and newer platforms with the ACPI CPPC (Collaborative Processor Performance Control), currently server platforms do not switch to AMD P-State by default, and no shared memory designs. AMD EPYC servers can still use AMD P-State if booting with an option such as amd_pstate=active.

By default with the AMD P-State driver the EPP/active mode is now the default mode of operation compared to the prior mode of "passive" or the Guided Autonomous Mode that was added in Linux 6.4. The active/EPP mode was added back in Linux 6.3 and helping to improve AMD CPU performance/power efficiency.

Phoronix benchmarks of the AMD P-State active mode compared to alternatives can be found in Ryzen Mobile Power/Performance With Linux 6.3's New AMD P-State EPP Driver.

The code with Linux 6.5 also adds a new X86_AMD_PSTATE_DEFAULT_MODE Kconfig switch if wishing to change the default mode of operation for the AMD P-State driver on supported platforms.

Over on the Intel power management side with Linux 6.5 is adding power-capping core support for Intel TPMI (Topology Aware Register and PM Capsule Interface) and a TPMI interface driver for the Intel RAPL (Runtime Average Power Limiting) code. There is also making intel_idle work to make it work with VM guests for hosts that cannot handle the MWAIT instruction.

The full list of power management updates for Linux 6.5 can be found via this pull request that already is merged to mainline.

There is also the ACPI pull that adds various ACPI backlight quirks, various other AMD quirk fixes, and other updates.