https://bugzilla.kernel.org/show_bug.cgi?id=19452
Summary: Fan control fails after wakeup from S3 on HP laptop
Compaq 6735b
Product: ACPI
Version: 2.5
Kernel Version: 2.6.36-rc6
Platform: All
OS/Version: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: Power-Fan
AssignedTo: acpi_power-...@kernel-bugs.osdl.org
ReportedBy: ullman.b...@gmx.de
Regression: No
After resuming from S3 the acpi fan control seems to be disabled. All
trip-points are ignored, if their temperature is reached.
Steps to Reproduce:
1) Suspend the machine.
2) Resume.
3) Do anything stressing, until a trip-point temperature is reached.
(I prefer make -j3 in a kernel-source-directory)
Actual results:
The fan remains on his state.
Expected results:
The fan should have increased its RPM.
Build Date & Platform:
Build 2010-09-31 on Gentoo Linux 10.0
Did not test this on other platforms.
Additional information:
My laptop fan has 5 states (FAN0-4).
On resuming it is always in the following state:
FAN0:off #loud
FAN1:off
FAN2:off
FAN3:on
FAN4:on # silent
At least this is, what is reported to the OS, actually it is always at the
state of FAN0. Doing an echo 3 > /proc/acpi/fan/FAN3/state after resuming will
fix this. The Fan state could be triggered by the BIOS, but this is just a
guess.
If the temperature reaches ca. 85°C, the fan is again triggered to the state of
FAN0, without the OS knowing about this. This could also be a BIOS mechanism,
as such temperatures can reduce hardware lifetime.
Hibernating works fine, as long as the system is hibernated of a clean session.
If the session was suspended before, the fan control won´t work on resume.
I can manually control the fan via the /proc/acpi/fan interface. Activating a
fan state works only, if the trip-point-temperature was reached.
i.e.:
The trip-point of FAN2 is 55°C. If I do an
echo 0 > /proc/acpi/fan/FAN2/state
while the temperature is <55°C this won´t have an effect.
If I do this while the temperature is >=55°C it will activate the fan state.
If you can´t confirm this, the bug could be specific to my laptop model
(wouldn´t be the first time).
Please tell me, if I can provide further information.
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