[Intel-gfx] [PATCH] drm/i915: Do not trigger the pageflip stall check too early

[Chris Wilson]

On Wed, Dec 17, 2014 at 04:41:42PM +0000, Chris Wilson wrote:
> On gen2-4, we have a separate pageflip prepare/finish phase. The intent
> of the stall check is to detect when we have incurred a delay,
> potentially indefinite, after the pageflip is submitted and before the
> flip is processed by the hardware. However, our notion of
> INTEL_FLIP_PENDING/INTEL_FLIP_COMPLETE do not tally with how we set the
> values during prepare/finish and the current stall check erroneously
> assumes that when the pending value >= COMPLETE, the driver has seen the
> hardware completion flag. But what the driver actually means, is that it
> has seen the acknowlegement that the flip is queued and is now pending
> the completion event.

Bah, otoh, as we don't mark the flip as pending before completion on
gen5+, we know don't detect when the flip is wedged there after applying
this patch.

It is quite possible that the work->pending check is entirely bogus.
Back to the drawing board.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre