Linux 6.10 Fixes AMD Zen 5 CPU Frequency Reporting With cpupower

Written by Michael Larabel in AMD on 6 June 2024 at 06:39 AM EDT. Add A Comment
This week's pull request of power management fixes for the Linux 6.10 kernel has an important change for the in-tree cpupower utility to fix P-State frequency reporting on upcoming Zen 5 (Family 1Ah) processors.

Now merged as part of the power management fixes is updating the cpupower utility to properly report P-State frequencies on AMD Zen 5 processors. This fix is for when using the ACPI CPUFreq driver. With newer AMD Ryzen processors defaulting to the AMD P-State driver, this change primarily is for AMD 5th Gen EPYC servers or others not opting to use the AMD P-State driver.

AMD 5th Gen EPYC graphic

As AMD CEO Dr. Lisa Su announced at Computex this week, look for 5th Gen EPYC servers in H2'2024 with up to 192 cores per socket.

Due to some MSR changes with AMD Family 1Ah and beyond, the cpupower driver needs some small changes to properly account for the P-State frequency.

The fix was merged to Linux 6.10 Git as part of this pull request. Presumably it will be back-ported as well to the stable kernel series. That pull also has a fix for the AMD P-State driver due to an inconsistency in the maximum frequency reported. The "scaling_max_freq" value was reported in MHz while the minimum and current frequencies are reported in KHz. Now the AMD P-State driver is changing scaling_max_freq to report in KHz as well so it matches the other sysfs values.
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