drm/atomic: Check for busy planes/connectors before setting the commit

We still want to fail with -EBUSY if a plane or connector is part of
a commit, even if it will be assigned to a new commit.

This closes a small hole left open where we should return -EBUSY.
It's not severe, because wait_for_dependencies and swap_state helpers
still block. But it should return -EBUSY and not stall.
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Fixes: 21a01abb ("drm/atomic: Fix freeing connector/plane state too early by tracking commits, v3.")
Link: https://patchwork.freedesktop.org/patch/msgid/20171016132928.6498-2-maarten.lankhorst@linux.intel.comReviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

drivers/gpu/drm/drm_atomic_helper.c

@@ -1772,16 +1772,16 @@ int drm_atomic_helper_setup_commit(struct drm_atomic_state *state,
 	}
 
 	for_each_oldnew_connector_in_state(state, conn, old_conn_state, new_conn_state, i) {
-		/* commit tracked through new_crtc_state->commit, no need to do it explicitly */
-		if (new_conn_state->crtc)
-			continue;
-
 		/* Userspace is not allowed to get ahead of the previous
 		 * commit with nonblocking ones. */
 		if (nonblock && old_conn_state->commit &&
 		    !try_wait_for_completion(&old_conn_state->commit->flip_done))
 			return -EBUSY;
 
+		/* commit tracked through new_crtc_state->commit, no need to do it explicitly */
+		if (new_conn_state->crtc)
+			continue;
+
 		commit = crtc_or_fake_commit(state, old_conn_state->crtc);
 		if (!commit)
 			return -ENOMEM;
@@ -1790,17 +1790,16 @@ int drm_atomic_helper_setup_commit(struct drm_atomic_state *state,
 	}
 
 	for_each_oldnew_plane_in_state(state, plane, old_plane_state, new_plane_state, i) {
-		/*
-		 * Unlike connectors, always track planes explicitly for
-		 * async pageflip support.
-		 */
-
 		/* Userspace is not allowed to get ahead of the previous
 		 * commit with nonblocking ones. */
 		if (nonblock && old_plane_state->commit &&
 		    !try_wait_for_completion(&old_plane_state->commit->flip_done))
 			return -EBUSY;
 
+		/*
+		 * Unlike connectors, always track planes explicitly for
+		 * async pageflip support.
+		 */
 		commit = crtc_or_fake_commit(state, new_plane_state->crtc ?: old_plane_state->crtc);
 		if (!commit)
 			return -ENOMEM;