https://bugzilla.kernel.org/show_bug.cgi?id=214205

            Bug ID: 214205
           Summary: thermal sensor broken after resume, fan speed at 100%
                    speed on Lenovo ThinkPad Carbon X1 4th Gen
           Product: ACPI
           Version: 2.5
    Kernel Version: 5.14.0-rc7.g61596f4
          Hardware: Intel
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: EC
          Assignee: acpi...@kernel-bugs.osdl.org
          Reporter: sbra...@suse.com
        Regression: No

On Lenovo ThinkPad Carbon X1 4th Gen, fan speed often raises to max after
resume.

Reproducibility varies, but recently I get about 85% reproducibility.

The problem never appears on boot from poweroff.

But when it appears after resume, reboot does not help. Shutdown is required to
get fan back to work properly.

It can be worked around by repeated suspend/resume many times:
cat /proc/acpi/ibm/thermal | ( read t x y ; echo $x ; if test "$x" = -128 ;
then systemctl suspend ; fi )

With ~1% probability, a different problem appears: Fan does not stop during
resume. It may be related.

Another strange ACPI behavior, much less annoying: The computer often forgets
wakeup preferences for USB devices during the suspend/wake cycle, e. g.
/sys/bus/usb/devices/1-4.2.1.2/power/wakeup goes from enabled to disabled.

It is caused by the failed resume of the thermal sensor, which returns -128
instead of the correct value.

cat /proc/acpi/ibm/thermal
When it fails:
temperatures:   -128 -128 0 0 0 0 0 0
When OK:
temperatures:   47 -128 0 0 0 0 0 0

sensors command shows the same problem.

Hardware:
ThinkPad X1 Carbon 4th
20FB002UMC
BIOS N1FET75W (1.49) 05/25/2021

Output of hwprobe:
https://linux-hardware.org/?probe=44d0412dd3

This bug is similar to bug 196129 for 5th Gen.

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