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

[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
you echo 0 there?

BR,
Jani.



-- 
Jani Nikula, Intel Open Source Technology Center