Bug#1125933: linux-image-6.12.63+deb13-amd64: Fan stuck on high speed, wont turn off even though cpu usage is normal

[Salvatore Bonaccorso <carnil@debian.org>]

Control: tags -1 + moreinfo

Hi,

On Mon, Jan 19, 2026 at 09:08:11AM +0100, Jim Christian Dale Haukvik wrote:
> Package: src:linux
> Version: 6.12.63-1
> Severity: important
> X-Debbugs-Cc: jchaukvik@gmail.com
> 
> Dear Maintainer,
> 
> What led up to the situation?
> I upgraded my system from Debian 13.2 to 13.3. This included a kernel update
> from version 6.12.57 to 6.12.63.
> 
> What exactly did you do (or not do) that was effective (or ineffective)?
> I booted into the new kernel (6.12.63). I checked CPU usage using htop, which
> was normal (under 5%), yet the fan remained at a high, constant speed.
> I then rebooted and selected the previous kernel version (6.12.57) from the
> GRUB advanced menu.
> 
> What was the outcome of this action?
> On kernel 6.12.57, the fan behaves normally (turning off or slowing down at
> idle). On kernel 6.12.63, the fans are not turning off.
> 
> What outcome did you expect instead?
> I expected the fan management to remain functional as they were in the previous
> kernel version. This appears to be a regression in the 6.12.63 build.

As, as far I understand you can reliably reproduce the problem, it
would be great if you could bisect the problem. That would involve
compiling and testing a few kernels:

    git clone --single-branch -b linux-6.12.y https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git
    cd linux-stable
    git checkout v6.12.57
    cp /boot/config-$(uname -r) .config
    yes '' | make localmodconfig
    make savedefconfig
    mv defconfig arch/x86/configs/my_defconfig

    # test 6.12.57 to ensure this is "good"
    make my_defconfig
    make -j $(nproc) bindeb-pkg
    ... install the resulting .deb package and confirm the problem does not exists

    # test 6.12.63 to ensure this is "bad"
    git checkout v6.12.63
    make my_defconfig
    make -j $(nproc) bindeb-pkg
    ... install the resulting .deb package and confirm the FAN problem exists

With that confirmed, the bisection can start:

    git bisect start
    git bisect good v6.12.57
    git bisect bad v6.12.63

In each bisection step git checks out a state between the oldest
known-bad and the newest known-good commit. In each step test using:

    make my_defconfig
    make -j $(nproc) bindeb-pkg
    ... install, try to boot / verify if problem exists

and if the problem is hit run:

    git bisect bad

and if the problem doesn't trigger run:

    git bisect good

. Please pay attention to always select the just built kernel for
booting, it won't always be the default kernel picked up by grub.

Iterate until git announces to have identified the first bad commit.

Then provide the output of

    git bisect log

In the course of the bisection you might have to uninstall previous
kernels again to not exhaust the disk space in /boot. Also in the end
uninstall all self-built kernels again.

Additionally to the above, could you please as well check if the
current version in unstable would expose as well the problem?

Regards,
Salvatore