2014-11-01 13:41:17

by Ortwin Glück

Subject: [drm] 3.18 regression: backlight dark after resume

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 <[email protected]>
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 <[email protected]>
Reviewed_by: Clinton Taylor <[email protected]>
Tested_by: Clinton Taylor <[email protected]>
Signed-off-by: Daniel Vetter <[email protected]>


Thanks,

Ortwin

2014-11-03 10:34:25

by Jani Nikula

Subject: Re: [drm] 3.18 regression: backlight dark after resume

On Sat, 01 Nov 2014, Ortwin Glück <[email protected]> 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 <[email protected]>
> 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 <[email protected]>
> Reviewed_by: Clinton Taylor <[email protected]>
> Tested_by: Clinton Taylor <[email protected]>
> Signed-off-by: Daniel Vetter <[email protected]>

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