On Wed, Aug 26, 2015 at 11:41 AM, 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.
So, I expect msm should actually be able to do this w/ dual-dsi (where
we are using two CRTC's, w/ synchronized flushes)..
Probably someone who has a dual-dsi panel should actually test that to
confirm. But it seems like it should work. Maybe we need something
in 'struct drm_crtc' so core can realize that two CRTC's are locked
together..
BR,
-R
> I've put this into the core since I really couldn't come up with a
> case where we don't want to enforce that. But if that ever happens it
> would be easy to move this check into helpers.
>
> 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.
>
> Cc: Thierry Reding <thierry.reding@xxxxxxxxx>
> Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
> Cc: Daniel Stone <daniels@xxxxxxxxxxxxx>
> Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
> ---
> drivers/gpu/drm/drm_atomic.c | 22 ++++++++++++++++++++++
> 1 file changed, 22 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index 434915448ea0..f27aae3fa765 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -663,6 +663,22 @@ drm_atomic_plane_get_property(struct drm_plane *plane,
> return 0;
> }
>
> +static bool
> +plane_switching(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;
> +
> + return true;
> +}
> +
> /**
> * drm_atomic_plane_check - check plane state
> * @plane: plane to check
> @@ -734,6 +750,12 @@ static int drm_atomic_plane_check(struct drm_plane *plane,
> return -ENOSPC;
> }
>
> + if (plane_switching(state->state, plane, state)) {
> + DRM_DEBUG_ATOMIC("[PLANE:%d] switching CRTC directly\n",
> + plane->base.id);
> + return -EINVAL;
> + }
> +
> return 0;
> }
>
> --
> 2.5.0
>
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