[Intel-gfx] 3.0 (or SNA?) regression: failed to train DP, aborting

[Andrew Lutomirski]

I have a Q67 (DQ67SW board) attached to a Dell U2711 via DP.  In
previous kernels, the DP link has worked flawlessly.  I just booted
3.0-final and simultaneously enabled SNA, and now when my screen goes
to sleep I don't get an image back until I power cycle the monitor.
dmesg says:

[drm:intel_dp_complete_link_train] *ERROR* failed to train DP, aborting

I don't know whether this is a 3.0 regression or whether it's
triggered by SNA, but something broke.

--Andy