Created attachment 117641 [details]
dmesg with drm.debug=14

My setup: Thinkpad T440p with an Ultra Dock, two identical displays connected to the dock. DP2-1 connected via a DP-DVI converter to the docks' display port socket, DP2-2 connected directly to the dock's DVI port.

DP2-1 gets the wrong resolution; "xrandr --verbose" shows that no EDID data are available. I can manually add the correct resolution with "xrandr --addmode", which makes the display work on the correct resolution.

I can swap the displays physically, and the one connected to the DVI port always gets the correct resolution - so it is not a display issue.

I connected the display via a MiniDP-DVI adapter directly to the laptop (bypassing the docking station) and it got the correct resolution.


Attached is dmesg output with drm.debug=14


Xorg server: 1:7.7+1ubuntu8.1
xf86-video-intel: git 2015-07-31 17:17, bc063c9f4af90542297877281b1b9f4692dafde4
Linux kernel: Linux csystems 4.1.4-dp-mst #1 SMP Fri Aug 7 09:25:36 CEST 2015 x86_64 x86_64 x86_64 GNU/Linux