On Wed, Aug 26, 2015 at 05:51:46PM -0400, Rob Clark wrote:
> On Wed, Aug 26, 2015 at 3:49 PM, Daniel Vetter <daniel.vetter@xxxxxxxx> wrote:
> > Very strictly speaking this is possible if you have special hw and
> > genlocked CRTCs. In general switching a plane between two active CRTC
> > just won't work so well and is probably not tested at all. Just forbid
> > it.
> >
> > I've put this into the core since right now no helper or driver copes
> > with it, no userspace has code for it and no one asks for it. Yes
> > there's piles of corner-cases where this would be possible to do this
> > like:
> > - switch from inactive crtc to active crtc
> > - swithc from active crtc to inactive crtc
> > - genlocked display
> > - invisible plane (to do whatever)
> > - idle plane hw due to dsi cmd mode/psr
> > - whatever
> > but looking at details it's not that easy to implement this correctly.
> > Hence just put it into the core and add a comment, since the only
> > userspace we have right now for atomic (weston) doesn't want to use
> > direct plane switching either.
>
> I suspect that eventually we'll want to make this a helper exposed to
> drivers and push this check down into the drivers.. perhaps that is
> not until weston (and/or atomic based hwc) grows driver specific
> userspace plugin type API to make smarter hw specific decisions..
> until then, this is probably the most reasonable thing to do.. so
Yeah this really is just to plug a "undefined behaviour" gap in the abi
until we know what exactly we want and have some userspace needing this.
> (w/ s/swihc/switch/ fix smashed in above)
>
> Reviewed-by: Rob Clark <robdclark@xxxxxxxxx>
Fixed&merged to drm-misc, thanks for the review.
-Daniel
>
>
> > v2: don't bother with complexity and just outright disallow plane
> > switching without the intermediate OFF state. Simplifies drivers, we
> > don't have any hw that could do it anyway and current atomic userspace
> > (weston) works like this already anyway.
> >
> > v3: Bikeshed function name (Ville) and add comment (Rob).
> >
> > v4: Also bikeshed commit message (Rob).
> >
> > Cc: Thierry Reding <thierry.reding@xxxxxxxxx>
> > Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
> > Cc: Daniel Stone <daniels@xxxxxxxxxxxxx>
> > Acked-by: Daniel Stone <daniels@xxxxxxxxxxxxx>
> > Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
> >
> > ---
> >
> > Imo this is bikeshedded enough, so either someone takes this or
> > someone else can mangle this patch more.
> > -Daniel
> > ---
> > drivers/gpu/drm/drm_atomic.c | 27 +++++++++++++++++++++++++++
> > 1 file changed, 27 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> > index 1066e4b658cf..40ddd6aa100f 100644
> > --- a/drivers/gpu/drm/drm_atomic.c
> > +++ b/drivers/gpu/drm/drm_atomic.c
> > @@ -663,6 +663,27 @@ drm_atomic_plane_get_property(struct drm_plane *plane,
> > return 0;
> > }
> >
> > +static bool
> > +plane_switching_crtc(struct drm_atomic_state *state,
> > + struct drm_plane *plane,
> > + struct drm_plane_state *plane_state)
> > +{
> > + struct drm_crtc_state *crtc_state, *curr_crtc_state;
> > +
> > + if (!plane->state->crtc || !plane_state->crtc)
> > + return false;
> > +
> > + if (plane->state->crtc == plane_state->crtc)
> > + return false;
> > +
> > + /* This could be refined, but currently there's no helper or driver code
> > + * to implement direct switching of active planes nor userspace to take
> > + * advantage of more direct plane switching without the intermediate
> > + * full OFF state.
> > + */
> > + return true;
> > +}
> > +
> > /**
> > * drm_atomic_plane_check - check plane state
> > * @plane: plane to check
> > @@ -734,6 +755,12 @@ static int drm_atomic_plane_check(struct drm_plane *plane,
> > return -ENOSPC;
> > }
> >
> > + if (plane_switching_crtc(state->state, plane, state)) {
> > + DRM_DEBUG_ATOMIC("[PLANE:%d] switching CRTC directly\n",
> > + plane->base.id);
> > + return -EINVAL;
> > + }
> > +
> > return 0;
> > }
> >
> > --
> > 2.5.0
> >
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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