On Mon, Oct 10, 2016 at 02:46:35PM +0200, Daniel Vetter wrote:
> On Mon, Oct 10, 2016 at 2:19 PM, <ville.syrjala@xxxxxxxxxxxxxxx> wrote:
> > From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> >
> > We don't want all planes to be added to the state whenever a
> > plane with fixed zpos gets enabled/disabled. This is true
> > especially for eg. cursor planes on i915, as we want cursor
> > updates to go through w/o throttling. Same holds for drivers
> > that don't support zpos at all (i915 actually falls into this
> > category right now since we've not yet added zpos support).
> >
> > Allow drivers more freedom by letting them deal with zpos
> > themselves instead of doing it in drm_atomic_helper_check_planes()
> > unconditionally. Easiest solution seems to be to move the call
> > up to drm_atomic_helper_check(). But as some drivers might want
> > to use that function without the zpos handling, let's provide
> > two variants: the normal one, and one that deals with zpos.
> >
> > Cc: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> > Cc: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxx>
> > Cc: Vincent Abriou <vincent.abriou@xxxxxx>
> > Cc: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> > Cc: Inki Dae <inki.dae@xxxxxxxxxxx>
> > Cc: Joonyoung Shim <jy0922.shim@xxxxxxxxxxx>
> > Cc: Seung-Woo Kim <sw0312.kim@xxxxxxxxxxx>
> > Cc: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
> > Cc: Lyude <cpaul@xxxxxxxxxx>
> > Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx
> > Fixes: 44d1240d006c ("drm: add generic zpos property")
> > Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
>
> Seems a bit fragile, and then drivers still need to not overshot when
> they do zpos (which we want eventually in i915 too).
The only platform where we can do it is pre-g4x, and vlv/chv. And I'm
thinking I can do a better job of it in the driver.
> I think the
> proper way is to keep track of a per-plane zpos changed (or compute
> that ad-hoc, we have both states). And only grab more planes if a zpos
> value changed.
Doesn't work with normalized zpos. The plane's actual zpos may be
unchanged even if the normalized zpos changes.
>
> That would fix the issue at the source, also work for us in the
> future, and it should be contained to just the helper function itself.
> Win all around ;-)
> -Daniel
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch
--
Ville Syrjälä
Intel OTC
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