[Intel-gfx] [RFC] Async flips

[Jesse Barnes]

On Wed, 31 Oct 2012 14:53:24 +0200
Ville Syrjälä <ville.syrjala at linux.intel.com> wrote:

> On Tue, Oct 30, 2012 at 01:33:47PM -0500, Jesse Barnes wrote:
> > The hw supports async flips through the render ring, so why not expose it?
> > It gives us one more "tear me harder" option we can use in the DDX and
> > for other cases where simply flipping to the latest buffer is more
> > important than visual quality.
> 
> The only reason I can see why anyone would really want async flips is
> when you're restricted to double buffering. With triple buffering you
> should be able to override the previous flip w/o tearing.
> 
> Well, actually if you use the ring based flips, then you can't do the
> override. My atomic page flip code can do it because it's using mmio
> flips. There were also other reasons favoring mmio over ring.
> 
> Once the atomic code is deemed ready, I would suggest we just nuke the
> ring based flip code (pun intended).

Yeah, I agree.  In fact one of the first versions of the flip code used
mmio, and I think it's a better way to go.

I think you're correct about triple buffering, but I don't know if our
DDX does the right thing here these days or not (by default).

-- 
Jesse Barnes, Intel Open Source Technology Center