[Intel-gfx] [PATCH] drm/i915: Use RCS flips on Ivybridge+

[Chris Wilson]

On Tue, Aug 20, 2013 at 01:39:02PM +0100, Chris Wilson wrote:
> On Tue, Aug 20, 2013 at 02:31:03PM +0200, Daniel Vetter wrote:
> > On Tue, Aug 20, 2013 at 10:34 AM, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> > > RCS flips do work on Iybridge+ so long as we can unmask the messages
> > > through DERRMR. However, there are quite a few workarounds mentioned
> > > regarding unmasking more than one event or triggering more than one
> > > message through DERRMR. Those workarounds in principle prevent us from
> > > performing pipelined flips (and asynchronous flips across multiple
> > > planes) and equally apply to the "known good" BCS ring. Given that it
> > > already appears to work, and also appears to work with unmasking all 3
> > > planes at once (and queuing flips across multiple planes), be brave.
> > >
> > > Bugzlla: https://bugs.freedesktop.org/show_bug.cgi?id=67600
> > > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > 
> > Can you pls add some words with how this DERRMR write will interact
> > with scanline waits from SNA? I think just a few words to explain how
> > switching from scanline waits and blits to pageflips and back would be
> > good (even though I don't really expect that to happen often,
> > especially now that we have the buffer age extension and friends).
> 
> The DERRMR is overwritten by each before use. I thought that was
> self-explanatory.

The not-so-self-explanatory part is that there is a implicit
synchronisation point in userspace between switching between flips and
scanlines.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre