Created attachment 117134 [details]
more debug output with successful and unsuccessful link training

I applied both debug output patches. (the second one doesn’t apply cleanly
anymore)
An external monitor is connected via the mini vga port so i can still do
something. 
Directly after startup i have a blackscreen on the internal display but the
external display shows the tty. 
After login i start X with gnome. Within gnome I switch between display modes
(mirror, switch which is primary display) and it eventually works.