[Bugme-new] [Bug 19452] New: Fan control fails after wakeup from S3 on HP laptop Compaq 6735b

bugzilla-daemon at bugzilla.kernel.org bugzilla-daemon at bugzilla.kernel.org
Fri Oct 1 15:27:02 PDT 2010


           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-fan at kernel-bugs.osdl.org
        ReportedBy: ullman.bugs at 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
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

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.
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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