AMD Linux CPU Temperature Driver Sees Latest Patches For Zen 4 & Likely Mendocino

One of my personal gripes with AMD's Zen CPU support on Linux has been the lack of timely support for CPU temperature monitoring with their "k10temp" driver. Even though usually just new IDs are often needed and sometimes needing to adjust offsets or other minor changes, it has traditionally been done post-launch and sometimes left up to patches from the open-source community. Thankfully that has been changing and with Zen 4 it looks like that support will be ready for launch-day with the mainline Linux kernel.

AMD with Rembrandt (Yellow Carp) they managed to land the k10temp support pre-launch and for Zen 4 they have also been working for some time now on ensuring CPU temperature monitoring on Linux is working... It's certainly not critical for most users, but a personal frustration since for launch-day CPU reviews it's great including thermal data that hasn't been possible when requiring more than the new IDs when in the past there were at times questions over offsets, etc. While on the AMD side, it's not a huge engineering effort but something that pleases tech-minded Linux enthusiasts.

Going back to last year AMD was preparing for next-gen CPUs with k10temp changes to support up to 12 CCDs and making other driver patches for new PCI IDs. Out today is the latest patch series for k10temp in preparing the Zen 4 support.

The patches going back to last year cited new Family 19h Models while now it turns out some model IDs were missing. The patch series from AMD Linux engineer Mario Limonciello explains, "This series started as what looked like a correction to previous commits, but I missed that the previous commits were for a different family with the same chip models. So while fixing up the series I also noticed that a few upcoming chips have new PCIe IDs and CCD offsets not yet supported, so add them to amd_nb/k10temp."

Lisa Su showing off Zen 4 back during her Computex 2022 keynote.

What this fifth iteration of the k10temp enablement patches amounts to is supporting Family 17h A0h-AFh, Family 19h 70h-7Fh, and Family 19h 60h-6Fh. Family 17h is for Zen / Zen 2 while Family 19h so far is for Zen 3. As noted in prior Phoronix articles, based on other Linux kernel patches, it almost definitely appears Family 19h will include Zen 4 CPUs so all indications so far have been the 60h and 70h parts are likely for different Zen 4 (and Zen 4C) chips. The new IDs in Family 17h are presumably for the upcoming Mendocino SoCs for budget laptops... Otherwise I can't think of what other Zen 2 processors are currently not covered by the k10temp Linux driver support.

In any case, the v5 patches are now out there with the AMD Linux temperature driver "k10temp" ready to support these upcoming processors. Hopefully these patches will manage to land for the upcoming Linux 5.20 cycle so that there is the mainlined kernel support ahead of the Zen 4 desktop and server processor launches later this year.