Comment # 11 on bug 107978 from george

(In reply to Shmerl from comment #10)
> I just found something. My monitor - Dell U2413 has a setting for toggling
> DisplayPort 1.2. It was enabled until now. When I disable that setting, tty
> starts working!
> 
> My cable is supposed to support DP 1.2 and be Vesa compliant. It's Accel
> UltraAV DP 1.2 cable.
> 
> I hope this can help narrow down the problem.

Interesting, I have the exact same monitor, Dell U2413, I'll give this a try!