https://bugs.freedesktop.org/show_bug.cgi?id=73530
--- Comment #36 from Paul Menzel paulepanter@users.sourceforge.net --- (In reply to comment #35)
Created attachment 92230 [details] [review] possible fix
There's nothing in your logs indicating a link failure when setting up the DP link. It seems like your panel is just especially picky about the timing in the link training or something like that. Try the attached patch.
That patch did not help either. Rebooting the first time, the display was black and was working then after one xrandr off/auto cycle.
The second time I had to do 15 xrandr off/auto cycles.
I've also pushed a branch with some other DP related patches that might help if you want to try it: http://cgit.freedesktop.org/~agd5f/linux/log/?h=drm-next-3.14-wip
I did not tried that yet.