drm/atomic: Add sanity checks to drm_atomic_helper_async_commit()

->atomic_async_update() requires that drivers update the plane->state
object before returning. Make sure at least common properties have been
updated.

Cc: Gustavo Padovan <gustavo@padovan.org>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Acked-by: Eric Anholt <eric@anholt.net>
Acked-by: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20180330145518.29770-1-boris.brezillon@bootlin.com

drivers/gpu/drm/drm_atomic_helper.c

@@ -1572,6 +1572,17 @@ void drm_atomic_helper_async_commit(struct drm_device *dev,
 	for_each_new_plane_in_state(state, plane, plane_state, i) {
 		funcs = plane->helper_private;
 		funcs->atomic_async_update(plane, plane_state);
+
+		/*
+		 * ->atomic_async_update() is supposed to update the
+		 * plane->state in-place, make sure at least common
+		 * properties have been properly updated.
+		 */
+		WARN_ON_ONCE(plane->state->fb != plane_state->fb);
+		WARN_ON_ONCE(plane->state->crtc_x != plane_state->crtc_x);
+		WARN_ON_ONCE(plane->state->crtc_y != plane_state->crtc_y);
+		WARN_ON_ONCE(plane->state->src_x != plane_state->src_x);
+		WARN_ON_ONCE(plane->state->src_y != plane_state->src_y);
 	}
 }
 EXPORT_SYMBOL(drm_atomic_helper_async_commit);