AMD Updates P-State "Guided Autonomous Mode" Support For Linux

Back in December AMD posted P-State Linux driver patches for implementing a "Guided Autononmous Mode" of operation to complement the existing passive mode used by the amd_pstate driver and the pending fully-autonomous/EPP mode that has seen many patch revisions in recent months. While much of AMD's engineering focus has been on getting the P-State EPP code upstreamed, out today is the second iteration of that Guided Autonomous Mode support.

The AMD Guided Autonomous Mode support was summed up as: "OS scaling governor specifies min and max frequencies/ performance levels through `Minimum Performance` and `Maximum Performance` register, and PMFW can autonomously select an operating frequency in this range." Benchmarks posted by AMD with the Guided Autonomous Mode patches showed it performing well with the AMD 4th Gen EPYC "Genoa" processors and better than the default passive mode or using the generic ACPI CPUFreq driver.

While AMD has been working to get P-State EPP support upstreamed for Linux 6.3, the Guided Autonomous Mode patches were updated today and it's looking like they too could possibly follow suit into the next kernel version. The v2 patches don't have much in the way of changes besides fixing an issue with shared memory systems and then re-basing this code atop the latest EPP driver patches.

The v2 patches can be found on the mailing list for testing and hopefully this Guided Autonomous Mode and EPP work will both be ready in time for next month's Linux 6.3 cycle. Stay tuned and once this work is on approach for landing I'll be around with some fresh Linux power/performance benchmarks for both EPYC and Ryzen processors.