Linux 5.15 Hardware Monitoring Is Big But Overdue For AMD

The Linux 5.15 hardware monitoring "HWMON" subsystem changes were sent out and now merged for this next kernel version. Particularly notable this cycle is AMD catching up on some of their sensors support.

First up, this HWMON update is the one that finally adds Zen 3 APU temperature monitoring support. The Zen 3 APU temperature monitoring is only landing now for the Linux 5.15 cycle even though these APUs have been found in desktops and laptops for months. It was just missing the necessary model ID in the k10temp driver but wasn't addressed until a community member sent in the patch for adding it to the driver.

While it's unfortunate that the Zen 3 APU temperature monitoring support arrived post-launch and left up to the community once again, this same HWMON pull request is exciting in that it adds Yellow Carp APU temperature monitoring too. Yellow Carp looks like it may be the Ryzen 6000 mobile series, a.k.a. "Rembrandt", but in any case it's great to see it being pre-launch.

This Yellow Carp temperature monitoring support was submitted by one of the new additions to AMD's client CPU Linux team. That recent hire, Mario Limonciello, also added k10temp support for other missing AMD Zen 2/3 CPU entries plus also fixed up the driver to no longer display Tdie temperatures if there is no difference from the Tctl temperature.

Outside of the Ryzen client scope, the HWMON updates for Linux 5.15 also have a new driver on the AMD server side. New on the EPYC front is the AMD SB-RMI driver for the side-band remote management interface for out-of-band communication between the AMD SoC/CPU and the BMC via the APML/SBI. This new driver provides for the AMD SB-RMI sensor functionality around CPU socket power consumption, power limits, and maximum power limit. This SB-RMI driver will likely come in to play around OpenBMC support and more for AMD EPYC servers.

Linux 5.15 will help ensure your CPU is staying cool with AMD... Overdue support for existing APUs plus preparing now for future APUs. Plus the AMB SB-RMI driver on the EPYC side.

Beyond the AMD changes this cycle for HWMON, there is also a a new water cooling pump driver from the community. That latest addition is the Aquacomputer D5 Next. Other HWMON work includes Silicom N5010 PAC support in the Intel M10 BMC driver, fan control support for the Dell Precision 7510 via the Dell-SMM driver, and other small improvements/fixes throughout.

See the HWMON pull request for the full list of changes this cycle.