[Intel-gfx] [PATCH] drm/i915: Mask the ring->head offset using the ring->size

[Chris Wilson]

On Tue, 17 Jan 2012 11:14:04 +0000, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> On Tue, 17 Jan 2012 11:59:27 +0100, Daniel Vetter <daniel at ffwll.ch> wrote:
> > I guess this is just the usual "snb doesn't like being pushed to hard bug"
> > resulting in random crashes with confusing error_states. So I think I'll
> > drop this. Correct?
> 
> I could find no other reason for this to have any effect other than the
> hw not playing fair so don't apply it until some one else starts
> experiencing random hangs on their SNB and can confirm whether this
> patch helps.

The news is that the hw is indeed not playing fair, and we have some
substantial evidence that demonstrates the cause here is the
autoreported position of the head is completely bogus on SNB+.

See https://bugs.freedesktop.org/show_bug.cgi?id=45492
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre