After missing the Linux 6.2 kernel merge window, AMD’s P-State EPP (Energy Performance Preference) driver has now iterated to its ninth revision; on the basis of existing P-State driver support, it seems to be on track for Linux 6.3 merged successfully.

AMD Linux engineer Perry Yuan released the ninth version of the P-State EPP driver patch, which aims to improve the performance and power control of the existing and mainline AMD P-State drivers. This functionality builds on the ACPI CPPC EPP knob.

This patch set implements a new AMD CPU frequency driver amd-pstate-epp instance for better performance and power control. CPPC has a parameter called energy preference performance (EPP). EPP is used in the CCLK DPM controller to drive the frequency at which a core will run during short periods of activity. EPP values ​​will be used for different operating system profiles (balanced, performance, power savings).

AMD Energy Performance Preference (EPP) provides a hint to the hardware, if the software wants to favor performance (0x0) or energy efficiency (0xff), the low-level power firmware will calculate the runtime frequency according to the EPP preference value. Therefore, the EPP hint will affect the frequency responsiveness of the CPU core.

Additionally, AMD Linux engineers have been working on P-State’s Guided Autonomous Mode.

Code updates have been made in the v9 patch set to address feedback raised in previous upstream code reviews, additional “reviewed-by” tags, and a few other fundamental fixes. According to technology website Phoronix, the AMD P-State EPP code seems to have finally settled down to improve the power/performance efficiency of modern Ryzen and EPYC processors. “Hopefully we’ll see them mainlined in Linux 6.3 to help improve performance in some areas where AMD P-State is currently used; there’s still a performance gap in those areas compared to the generic ACPI CPUFreq driver.”

See the kernel mailing list for more details.