[Intel-gfx] [RFC] drm/i915/skl: Use plane update function from mmio flips

[Chris Wilson]

On Tue, Apr 21, 2015 at 11:01:03AM +0100, Tvrtko Ursulin wrote:
> 
> Hi,
> 
> On 04/21/2015 10:51 AM, Chris Wilson wrote:
> >On Tue, Apr 21, 2015 at 10:29:52AM +0100, Tvrtko Ursulin wrote:
> >>From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> >>
> >>Avoids duplicating the code.
> >>
> >>Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> >>Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> >>Cc: Sonika Jindal <sonika.jindal at intel.com>
> >>Cc: Damien Lespiau <damien.lespiau at intel.com>
> >>---
> >>Can we do this?
> >
> >Sure, but I'd like to see update_primary_plane split into two in that
> >case. One to precalcuate the parameters, then the second to apply them
> >as we skip the first here (due to doing the setup in process context)
> >and want the second to run inside the vblank evasion logic (and the
> >unbounded nature of the current update_primary_plane logic scares me).
> 
> What part is unbounded? I don't see anything blocking?

The GTT view lookup may have to search through an arbitrary list, it's
even controllable by the user. Expect synmark nastiness. This is
"trivially" fixable, but this is only the current issue. The bigger issue
is simply that we have not said that this is a timing critical function
and now we are intending to use it from such a context.
 
> As a side note, watermarks seem to be not handled at all in the flip
> path as well...

The flip path should reject anything that requires a change in line size
i.e. a change in WM.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre