thinkpad_acpi fan stop working problem (was after resume) (speed becomes 65535)

[r ll <crquan@gmail.com>]

To THINKPAD ACPI EXTRAS DRIVER authors and related mailer list,

(got this list from MAINTAINERS and thinkpad_acpi.c)


This problem occasionally happens on my Thinkpad T410 with some recent kernels,
I remember this problem since 2.6.35 when I was installing Ubuntu-10
and now I have switched to Arch Linux with self complied latest
3.4-rc5, this issue
is remaining there,

most of time the fan is working well, but usually every night I close the laptop
let the Linux suspend; then resume on next morning, occasionally the laptop
could become very hot, usually above 90℃ for long time, if I compile something
or do some heavy work, it may go up over 128℃ then machine
automatically shutdown,

# cat /sys/devices/platform/thinkpad_hwmon/temp1_input
97000
# cat /sys/devices/platform/thinkpad_hwmon/fan1_input
65535

I guess the fan is actually not working at all;
I tried unload & reload the kernel module but it still doesn't work;
I tried manually set a speed level but it's still 65535, the machine
is still hot

# modprobe -r thinkpad_acpi && modprobe thinkpad_acpi fan_control=1

# echo 'level full-speed' >/proc/acpi/ibm/fan
# cat /proc/acpi/ibm/fan
status:		enabled
speed:		65535
level:		disengaged
commands:	level <level> (<level> is 0-7, auto, disengaged, full-speed)
commands:	enable, disable
commands:	watchdog <timeout> (<timeout> is 0 (off), 1-120 (seconds))


It seems the only way is to complete power off Linux for a few
seconds, power on again
then the fan could be working, I observed a normal speed should be
between 3000 ~ 5000, and machine temperature is 40~70℃, normally working;


Wonder if someone experienced same problem and how can we fix it?



at least to know how can I recover the fan to work, without rebooting



Thanks,