[Intel-gfx] [drm] 3.18 regression: backlight dark after resume

[Jani Nikula]

On Sat, 01 Nov 2014, Ortwin Glück <odi at odi.ch> wrote:
> Hi,
>
> Since 3.18-rc1 backlight is dark after resume from suspend. This is on a Samsung 
> laptop with i5 IvyBridge
>
> 00:02.0 VGA compatible controller: Intel Corporation 3rd Gen Core processor 
> Graphics Controller (rev 09)
>
>
> I have bisected this problem to the following commit:
> 73580fb764c4213d305c0d36bd8f856ae631eb42 is the first bad commit
> commit 73580fb764c4213d305c0d36bd8f856ae631eb42
> Author: Jani Nikula <jani.nikula at intel.com>
> Date:   Tue Aug 12 17:11:41 2014 +0300
>
>      drm/i915/dp: make backlight bl_power control power sequencer backlight
>
>      This lets the userspace switch off the backlight using the backlight
>      class sysfs bl_power file. The switch is done using the power sequencer;
>      the backlight PWM, and everything else, remains enabled. The display
>      backlight won't draw power, but for maximum power savings the encoder
>      needs to be switched off.
>
>      Signed-off-by: Jani Nikula <jani.nikula at intel.com>
>      Reviewed_by: Clinton Taylor <Clinton.A.Taylor at intel.com>
>      Tested_by: Clinton Taylor <Clinton.A.Taylor at intel.com>
>      Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>

See https://bugs.freedesktop.org/show_bug.cgi?id=80773 (please ignore
comments up to #10 or so).

Please attach dmesg with drm.debug=14 module parameter set, from boot to
suspend/resume and the problem, running the debug patch from comment
#18. Preferrably please attach the dmesg on the bug to keep everything
in one place.

Thanks,
Jani.


-- 
Jani Nikula, Intel Open Source Technology Center