[PATCH weston 0/3 v2] DRM lease support

Daniel Vetter daniel at ffwll.ch
Tue Feb 20 16:19:41 UTC 2018

On Tue, Feb 13, 2018 at 11:08:38AM +0000, Daniel Stone wrote:
> Hi all,
> On 13 February 2018 at 11:02, Marius-cristian Vlad
> <marius-cristian.vlad at nxp.com> wrote:
> > The sample client I've posted seems to be using the overlay plane.
> > Also, Daniel Stone confirmed a while back that they can be used.
> >
> > However it seems that page flipping on the overlay plane can not
> > be used if the connector is used in the same time (and I'm not
> > treating that case -- I disable that connector before handling out the
> > lease). Or primary plane -> page flipping, overlay -> wait for vblank?
> >
> > Looking briefly over weston code I see that for overlay planes they use
> > wait for vblank mechanism. Maybe Daniel/Pekka can confirm this, or
> > maybe this is an issue with legacy API and atomic doesn't suffer from
> > this problem. I'm not 100% sure.
> >
> > I guess it would be interesting to see if we can use it in the same
> > time.
> With the atomic API at least, overlay planes cannot be driven
> separately from other planes on that CRTC. Atomic only allows one
> commit per CRTC per vblank: either you hand out CRTCs in their
> entirety, or when you lease an overlay plane to a client, you stop
> updating anything else on that CRTC.

We've been talking about exposing async flips more generally, which (under
some driver-specific circumstances at least) could bypass the one per-crtc
commit queue that atomic has. That would allow us to hand out overlay
planes using leases, while the compositor still composites everything

But that's a quite a bit away, and there isn't really any real code yet
for it.
Daniel Vetter
Software Engineer, Intel Corporation

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