Arch Linux

Description:

On a thinkpad X270 which usually triggers the fan briefly and rarely except under very high load, the fan runs continuously following sleep, though the machine is cold. Rebooting does not change this, though powering off and on again does (until the next sleep).

I think this is due to a failed thermal sensor reading, possibly by thinkpad_acpi, which causes the acpitz-acpi-0 value to remain 'stuck' at a default 48 degrees.

Usually, thinkpad-isa-0000 returns N/A only for temp2 in the output of sensors, for example. temp1 generally has some plausible value. Prior to sleep, for example, I have

thinkpad-isa-0000
Adapter: ISA adapter
fan1: 0 RPM
temp1: +33.0°C
temp2: N/A
temp3: +0.0°C
temp4: +0.0°C
temp5: +0.0°C
temp6: +0.0°C
temp7: +0.0°C
temp8: +0.0°C
temp9: +0.0°C
temp10: +0.0°C
temp11: +1.0°C
temp12: +0.0°C
temp13: +0.0°C
temp14: +0.0°C
temp15: +0.0°C
temp16: +0.0°C

and

acpitz-acpi-0
Adapter: ACPI interface
temp1: +33.0°C (crit = +128.0°C)


whereas following sleep I have

thinkpad-isa-0000
Adapter: ISA adapter
fan1: 6185 RPM
temp1: N/A
temp2: N/A
temp3: +0.0°C
temp4: +0.0°C
temp5: +0.0°C
temp6: +0.0°C
temp7: +0.0°C
temp8: +0.0°C
temp9: +0.0°C
temp10: +0.0°C
temp11: +0.0°C
temp12: +0.0°C
temp13: +0.0°C
temp14: +0.0°C
temp15: +0.0°C
temp16: +0.0°C

and

acpitz-acpi-0
Adapter: ACPI interface
temp1: +48.0°C (crit = +128.0°C)

This remains at 48, as far as I can tell, regardless. Removing thinkpad_acpi and reloading it makes no difference.

The contents of /proc/acpi/ibm/thermal reflects the sensors output:

temperatures: -128 -128 0 0 0 0 0 0 0 0 1 0 0 0 0 0

as, I think, do /sys/devices/platform/thinkpad_hwmon/hwmon/hwmon7/temp*

0
1000
0
0
0
0
0
cat: /sys/devices/platform/thinkpad_hwmon/hwmon/hwmon7/temp1_input: No such device or address
cat: /sys/devices/platform/thinkpad_hwmon/hwmon/hwmon7/temp2_input: No such device or address
0
0
0
0
0
0
0

That is, temp1_input seems to go AWOL during sleep.

This seems eerily similar to a kernel bug from a while back, though that one didn't affect me:

https://bugzilla.kernel.org/show_bug.cgi?id=191181
https://bugzilla.kernel.org/show_bug.cgi?id=196129
https://bugzilla.kernel.org/attachment.cgi?id=256927&action=diff

There was a discussion about that problem on the forums at https://bbs.archlinux.org/viewtopic.php?id=224727.

However, that was all supposed to be fixed long ago, but the similarity and involvement of 48 degrees makes me wonder if this might be a regression?


Additional info:
* linux 5.11.4.arch1-1
* Hardware: Lenovo ThinkPad x270 | Intel(R) Core(TM) i5-7200U CPU @ 2.50GHz | Intel Corporation Wireless 8265 / 8275 | US keyboard with Euro | 512G NVMe INTEL SSDPEKKF512G7L

Steps to reproduce:
1. Acquire or possess a suitable ThinkPad.
2. Install Arch.
3. Boot machine.
4. Put machine to sleep.
5. Wake machine.
Optional: repeat steps 4 and 5 as desired.
Optional: reboot without powering off.