https://bugzilla.kernel.org/show_bug.cgi?id=96881
Bug ID: 96881
Summary: HP Compaq 6735s fan issues
Product: ACPI
Version: 2.5
Kernel Version: 3.19.4-1
Hardware: All
OS: Linux
Tree: Mainline
Status: NEW
Severity: high
Priority: P1
Component: Power-Fan
Assignee: [email protected]
Reporter: [email protected]
Regression: No
The fan on this laptop behaves very strangely.
Basically, it works like this:
- the fan is set according to the temperature the computer was at when it woke
up (or turned on)
- the fan speed doesn't change, except when it's done explicitly by the BIOS
when the temperature passes 80° - it then blows up the fan to full speed, until
it gets down to 70 or 75 °C (I'm not sure which)
- the fan maximum speed is also set by the temperature on wake (see below)
There are 6 cooling devices in `/sys/devices/virtual/thermal/`. I don't know
what 0 is, but 1 is the screen brightness. 2-5 seem to represent fan speeds,
where 5 is the lowest speed, and 2 is the highest.
Right now I'm using a script that looks like this:
'''
#!/bin/sh
echo -n 0 > /sys/devices/virtual/thermal/cooling_device5/cur_state
echo -n 0 > /sys/devices/virtual/thermal/cooling_device4/cur_state
echo -n 0 > /sys/devices/virtual/thermal/cooling_device3/cur_state
echo -n 0 > /sys/devices/virtual/thermal/cooling_device2/cur_state
echo -n 1 > /sys/devices/virtual/thermal/cooling_device5/cur_state
echo -n 1 > /sys/devices/virtual/thermal/cooling_device4/cur_state
echo -n 1 > /sys/devices/virtual/thermal/cooling_device3/cur_state
echo -n 1 > /sys/devices/virtual/thermal/cooling_device2/cur_state
'''
I call it every minute (as root).
It turns off the fan completely, and then adds speed. Something won't let it
behind a certain limit (it usually doesn't go all the way to 1111, but stops at
0011 or 0111), and that limit is usually the speed the fan should be at.
To an observer the fan just changes speeds with this script. It doesn't turn
off for a moment or whatever, it just goes faster or slower as it's supposed
to.
HOWEVER, there seems to be a hard limit, which is set by the temperature at
wake. If the temperature is very low (e.g. when I wake my laptop from sleep
after letting it sleeping for a long time), the limit is on 0001 and sometimes
even 0000. The laptop then gets hotter and hotter until the BIOS doesn't turn
up the emergency cooling (full speed fan when 85°C are reached). When the
laptop cools to ~75°C, it turns off again.
The only solution is to wake it up at a higher temperature.
NOTE0: Sometimes, on wake the fan is improperly set, especially in high
temperatures. The kernel sets it quite low, but as soon as the script runs it
goes quiet quick to get the temperature down.
NOTE1: The cooling device order isn't always as above. Rarely it mixes up, and
then the script flashes every minute because of the script. To solve it, I have
to reboot.
Without this hard limit, this laptop would be completely usable with the above
script. It is a real pain in the butt to suspend and wake the laptop all the
time just to get the temperature right.
If you need any more info, just ask.
Thanks.
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