On Thu, 06 Nov 2014, Arnd Hannemann arnd@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.