[Intel-gfx] [PATCH] drm/i915: dump even more into the error_state

[Ben Widawsky]

On Wed, Feb 01, 2012 at 10:26:45PM +0100, Daniel Vetter wrote:
> Chris Wilson and me have again stared at funny error states and it's
> been pretty clear from the start that something was seriously amiss.
> The seqnos last seen by the cpu were a few hundred behind those that
> the gpu could have possibly emitted last before it died ...
> 
> Chris now tracked it down (hopefully, definit verdict's still out),
> but in hindsight we'd have found the bug by simply dumping the cpu
> side tracking of the ring head and tail registers.
> 
> Fix this and prevent an identical time-waster in the future.
> 
> Because the hangs always involved semaphores in one way or another,
> we've tried to dump the mbox registers, but couldn't find any
> inconsistencies. Still, dump them too.

How about we only do this if semaphores are actually enabled? I think
that will eliminate potential confusion.