drm/atomic: add drm_atomic_add_affected_planes

This is a convenience function to add all planes for a crtc,
similar to add_affected_connectors. This will be used in
drm_atomic_helper_check_modeset, but drivers can call it too
when they need to recalculate all state.
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
[danvet: Amend kerneldoc a bit.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/drm_atomic.c

@@ -955,6 +955,45 @@ drm_atomic_add_affected_connectors(struct drm_atomic_state *state,
 }
 EXPORT_SYMBOL(drm_atomic_add_affected_connectors);
 
+/**
+ * drm_atomic_add_affected_planes - add planes for crtc
+ * @state: atomic state
+ * @crtc: DRM crtc
+ *
+ * This function walks the current configuration and adds all planes
+ * currently used by @crtc to the atomic configuration @state. This is useful
+ * when an atomic commit also needs to check all currently enabled plane on
+ * @crtc, e.g. when changing the mode. It's also useful when re-enabling a CRTC
+ * to avoid special code to force-enable all planes.
+ *
+ * Since acquiring a plane state will always also acquire the w/w mutex of the
+ * current CRTC for that plane (if there is any) adding all the plane states for
+ * a CRTC will not reduce parallism of atomic updates.
+ *
+ * Returns:
+ * 0 on success or can fail with -EDEADLK or -ENOMEM. When the error is EDEADLK
+ * then the w/w mutex code has detected a deadlock and the entire atomic
+ * sequence must be restarted. All other errors are fatal.
+ */
+int
+drm_atomic_add_affected_planes(struct drm_atomic_state *state,
+			       struct drm_crtc *crtc)
+{
+	struct drm_plane *plane;
+
+	WARN_ON(!drm_atomic_get_existing_crtc_state(state, crtc));
+
+	drm_for_each_plane_mask(plane, state->dev, crtc->state->plane_mask) {
+		struct drm_plane_state *plane_state =
+			drm_atomic_get_plane_state(state, plane);
+
+		if (IS_ERR(plane_state))
+			return PTR_ERR(plane_state);
+	}
+	return 0;
+}
+EXPORT_SYMBOL(drm_atomic_add_affected_planes);
+
 /**
  * drm_atomic_connectors_for_crtc - count number of connected outputs
  * @state: atomic state

include/drm/drm_atomic.h

@@ -120,6 +120,10 @@ drm_atomic_set_crtc_for_connector(struct drm_connector_state *conn_state,
 int __must_check
 drm_atomic_add_affected_connectors(struct drm_atomic_state *state,
 				   struct drm_crtc *crtc);
+int __must_check
+drm_atomic_add_affected_planes(struct drm_atomic_state *state,
+			       struct drm_crtc *crtc);
+
 int
 drm_atomic_connectors_for_crtc(struct drm_atomic_state *state,
 			       struct drm_crtc *crtc);