[Intel-gfx] 3.18.0-rc3: i915: eDP connected Display stays blank

[Arnd Hannemann]

Hi,

thanks for your quick response.

Am 06.11.2014 um 10:39 schrieb Jani Nikula:
> On Thu, 06 Nov 2014, Arnd Hannemann <arnd at arndnet.de> wrote:
>> Hi,
>>
>> I have a Thinkpad T440s (Haswell) connected to two additional Monitors
>> via a Docking Station (MST).
>>
>> During Bootup all three displays work, even when X is started.
>> However, if the laptop display is turned off once (either because of
>> power saving, or via xrandr), it fails to "come back".
>> That is if I try to re-enable it the Display stays blank.
>> I believe this used to work in 3.17.
>>
>> Here is the xrandr Ouput of the edp, when its enabled (but staying blank):
>> Screen 0: minimum 8 x 8, current 3840 x 1200, maximum 32767 x 32767
>> eDP1 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 309mm x 175mm
>>    1920x1080      60.0*+   59.9
>>
>> here is the debug output, while trying to enable it:
>>
> 
> ...
> 
>> [  416.538848] [drm:intel_edp_backlight_power] panel power control backlight disable
>>
>>
>> I'm happy to provide further input.
> 
> What does cat /sys/class/backlight/intel_backlight/bl_power say? What if

root at kallisto:~# cat /sys/class/backlight/intel_backlight/bl_power
1

> you echo 0 there?

:-) Works my display comes back, when I echo 0 there.

Is user-space doing something wrong here?

Best regards
Arnd