[Intel-gfx] Regression in drm-intel caused by d91a2cb8e510

[Alan Stern]

Daniel:

I'm encountering a problem with the drm-intel-nightly branch in your
drm-intel repository.  The symptom is that when I boot my laptop, at
some point during the start-up procedure the screen goes totally blank,
as though the backlight were turned off, and it remains that way.  I
can't tell if the backlight really is off -- it may be that there's
just nothing being displayed -- and playing with the screen-brightness
function keys doesn't help.

Git bisect located the source of the problem as commit d91a2cb8e510
(drm/i915: Add 180 degree primary plane rotation support).  The problem
occurs when I boot a kernel built from that commit, and it doesn't
occur when I boot a kernel built from the preceding commit
(19ac737dc3c3).

If necessary, I can get debugging info by logging in over a network 
connection.  Tell me what you need.

Alan Stern