[Intel-gfx] [PATCH] UXA: Wait until a pageflip actually completes to report it.

[Chris Wilson]

On Wed, May 07, 2014 at 10:44:23PM -0700, Jamey Sharp wrote:
> On Wed, May 07, 2014 at 04:55:18PM +0100, Chris Wilson wrote:
> > On Mon, May 05, 2014 at 11:05:07PM -0700, Jamey Sharp wrote:
> > > UXA was reporting page-flip completion as soon as the flip was scheduled
> > > with the kernel, instead of waiting for the kernel to indicate that the
> > > flip had actually completed.
> > > 
> > > Moving the DRI2SwapComplete call to the right place fixes all of our
> > > Piglit tests for OML_sync_control when run on xf86-video-intel/UXA,
> > > aside from a bit of difficult-to-reproduce flakiness when using a
> > > divisor > 1.
> > 
> > The violation is intentional, as it gives us triple buffering by
> > default. It can be disabled.
> 
> As far as I can tell, this patch has no effect on triple-buffering. I
> verified that by logging new_front->handle in intel_do_pageflip: It
> rotates through three different BO's on successive flips.

The patch blocks clients in GetBuffers until the swap completes,
preventing them from rendering to the third buffer.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre