AMD Zen1/Zen2/Zen3 PowerCap RAPL Support Queued For Linux 5.11

The work reported on back in October for RAPL PowerCap patches for AMD Zen CPUs from Zen 1 through Zen 3 are set to arrive with Linux 5.11 in early 2021.

This work led by Google engineers allow the AMD Family 17h/19h RAPL (Runtime Average Power Limiting) support within the Linux kernel's power-capping framework in the PowerCap driver.

Those unfamiliar with Linux's power-capping framework can see the kernel.org documentation. To user-space this provides a consistent interface for the power information now for both Intel/AMD processors.

Up to now the PowerCap driver has been Intel-only but extended by Google to support AMD CPUs in the form of Zen 1 and newer. This patch has the Zen 1 / Zen 2 support while a follow-up patch adds the support for Family 19h (Zen 3) given the MSRs are identical to the earlier Zen CPUs.

These patches have been queued into the Linux power management "-next" branch making them Linux 5.11 material for when that merge window opens in December.

Along related lines and for those not aware, Linux 5.8 added the "AMD_Energy" driver for exposing CPU energy information to user-space via the hardware monitoring (HWMON) interfaces. Though at the moment that driver does not yet support Zen 3 processors.