Intel Raptorlakes Throttles below -27°C

[DFrisch93]

Description

We faced an issue with thermald in combination with Intel Raptor Lake I-Temp Processors. While doing some environmental testing, after reaching -27°C thermald and also sensors kinda bufferoverflows and returns 100°C (which is max) and begins to throttle.

We checked the IA32_THERM_STATUS register and we figured that the "Reading Valid"-Bit is set.

We already asked Intel's Customer Support (Case NR 00898772 if some of you guys have access to that) and they answered that they changed this registern from 7-Bit to 8-Bit with Tiger Lake, and with Raptor-Lake being the first "Embedded Processors" for a long time, i think this may have some caused issues with negativ temperature readings.

In addition, they told us to open a issue here in github.

Nevertheless we currently disabled thermald in our distribution and that kinda works-around the issue we face
Distribution in use: Ubuntu 24.04 LTS
Kernel in use: 6.8
thermald version: 2.5.6 (shipped with ubuntu 24.04)

On a sidenote: I think that problem also affects lm-sensors (which changed after hitting -27 immediatelly to 100°C and toggled a bit till it got colder [99°C ... 96°C])

Regarding the boot-tjunction we booted at 25°C Ambient temperature so it should not affect this issue.

Screenshots

[spandruvada]

Sorry for the delay here and was on vacation.
There was a kernel change for this :

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=be6bfb29c55e48567983e24aba7b6bf9a66a45ab
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=6ae0092ca7adfce79336c6525cb0da561ecd4f04

That addresses this 7 to 8 bit issue.
You should try to apply these patches to your kernel.