AMD Ready For Ryzen Linux Systems To Use AMD P-State Active Mode By Default

As a win for AMD Ryzen Linux systems for greater performance and power efficiency, AMD is ready to set their P-State driver's default operation mode to be the recently merged "active" mode for Ryzen laptops and desktops.

Merged back in Linux 6.3 was the AMD P-State EPP "active" mode to complement the earlier "passive" default mode for using this CPU frequency scaling driver on Zen 2 and newer platforms. EPP is short for the Energy Performance Preference (EPP) and provides a hardware hint whether the software is biased t oward performance or energy efficiency. This EPP value can be set via sysfs from Linux user-space so users/administrators can easily indicate whether they'd prefer the highest performance or maximum power-savings.

More details and benchmarks on the AMD P-State EPP/active performance can be found in Ryzen Mobile Power/Performance With Linux 6.3's New AMD P-State EPP Driver. (This P-State mode isn't to be confused with Guided Autonomous Mode that was added more recently in Linux 6.4.)

As an exciting patch series out today that happens to be on the Phoronix birthday is AMD feeling comfortable enough to default to the P-State EPP (active) mode moving forward. This will be done just for AMD Ryzen systems whether it be desktops or laptops. The new patches are checking whether the FADT indicates the system power management profile is for determining if a system is a server or not.

As part of today's patches is adding a new X86_AMD_PSTATE_DEFAULT_MODE Kconfig switch for setting the default mode of operation for the amd-pstate driver. By default the active/EPP mode will be used while can also opt for disabling it, passive mode, or guided autonomous mode to be used by default. The AMD P-State mode can still be changed dynamically at boot time but this now makes it easy to set a default mode for a kernel build.

More details via this patch series by AMD Linux client engineer Mario Limonciello. There's still time that we could potentially see this set of patches picked up in the power management subsystem's "-next" branch ahead of the Linux 6.5 kernel merge window otherwise would be deferred until v6.6 later this year. In any event, it's great seeing AMD comfortable enough to now enable AMD P-State active/EPP mode by default for client systems. As a reminder, this is only relevant for AMD Ryzen 3000 "Zen 2" and newer systems with the AMD P-State driver being contingent upon ACPI CPPC support.