A patch for the Intel P-State CPU frequency scaling Linux driver is pending to avoid confusing the processor firmware on newer platforms like Intel Core Ultra Series 3 "Panther Lake" where Dynamic Efficiency Control (DEC) is supported.

Intel Dynamic Efficiency Control is a newer power management feature to optimize energy use under light workloads. But it turns out the current Intel P-State driver handling can end up confusing the processor firmware in the presence of DEC.

Intel engineer and Linux power management subsystem maintainer Rafael Wysocki explained in today's patch:

"In principle, the desired performance level can be set in MSR_HWP_REQUEST to indicate to the processor what performance level the OS would like the given CPU to run at, but if the Dynamic Efficiency Control (DEC) feature is enabled in the processor, doing so may result in confusing the processor firmware. It is then better to let the processor firmware figure out the most suitable performance level by itself.

Accordingly, make intel_pstate always set the desired performance level to zero (which means "no preference") when running on a platform with DEC enabled."

[1]The patch is out on the mailing list. With the timing it's possible it still could be picked up in time for the upcoming Linux v7.3 merge window. No performance/power numbers were publicly provided as part of the patch to indicate the impact of confusing the processor firmware.



[1] https://lore.kernel.org/linux-pm/4758098.LvFx2qVVIh@rafael.j.wysocki/