drm: Introduce a drm_crtc_commit_wait helper

There's currently four users of the same logic to wait for a commit to
be flipped: three for the CRTCs, connectors and planes in
drm_atomic_helper_wait_for_dependencies, and one in vc4.

Let's consolidate this a bit to avoid any code duplication.
Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20210111084401.117152-1-maxime@cerno.tech

drivers/gpu/drm/drm_atomic.c

@@ -52,6 +52,45 @@ void __drm_crtc_commit_free(struct kref *kref)
 }
 EXPORT_SYMBOL(__drm_crtc_commit_free);
 
+/**
+ * drm_crtc_commit_wait - Waits for a commit to complete
+ * @commit: &drm_crtc_commit to wait for
+ *
+ * Waits for a given &drm_crtc_commit to be programmed into the
+ * hardware and flipped to.
+ *
+ * Returns:
+ *
+ * 0 on success, a negative error code otherwise.
+ */
+int drm_crtc_commit_wait(struct drm_crtc_commit *commit)
+{
+	unsigned long timeout = 10 * HZ;
+	int ret;
+
+	if (!commit)
+		return 0;
+
+	ret = wait_for_completion_timeout(&commit->hw_done, timeout);
+	if (!ret) {
+		DRM_ERROR("hw_done timed out\n");
+		return -ETIMEDOUT;
+	}
+
+	/*
+	 * Currently no support for overwriting flips, hence
+	 * stall for previous one to execute completely.
+	 */
+	ret = wait_for_completion_timeout(&commit->flip_done, timeout);
+	if (!ret) {
+		DRM_ERROR("flip_done timed out\n");
+		return -ETIMEDOUT;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_crtc_commit_wait);
+
 /**
  * drm_atomic_state_default_release -
  * release memory initialized by drm_atomic_state_init

drivers/gpu/drm/drm_atomic_helper.c

@@ -2202,70 +2202,27 @@ void drm_atomic_helper_wait_for_dependencies(struct drm_atomic_state *old_state)
 	struct drm_plane_state *old_plane_state;
 	struct drm_connector *conn;
 	struct drm_connector_state *old_conn_state;
-	struct drm_crtc_commit *commit;
 	int i;
 	long ret;
 
 	for_each_old_crtc_in_state(old_state, crtc, old_crtc_state, i) {
-		commit = old_crtc_state->commit;
-
-		if (!commit)
-			continue;
-
-		ret = wait_for_completion_timeout(&commit->hw_done,
-						  10*HZ);
-		if (ret == 0)
-			DRM_ERROR("[CRTC:%d:%s] hw_done timed out\n",
-				  crtc->base.id, crtc->name);
-
-		/* Currently no support for overwriting flips, hence
-		 * stall for previous one to execute completely. */
-		ret = wait_for_completion_timeout(&commit->flip_done,
-						  10*HZ);
-		if (ret == 0)
-			DRM_ERROR("[CRTC:%d:%s] flip_done timed out\n",
+		ret = drm_crtc_commit_wait(old_crtc_state->commit);
+		if (ret)
+			DRM_ERROR("[CRTC:%d:%s] commit wait timed out\n",
 				  crtc->base.id, crtc->name);
 	}
 
 	for_each_old_connector_in_state(old_state, conn, old_conn_state, i) {
-		commit = old_conn_state->commit;
-
-		if (!commit)
-			continue;
-
-		ret = wait_for_completion_timeout(&commit->hw_done,
-						  10*HZ);
-		if (ret == 0)
-			DRM_ERROR("[CONNECTOR:%d:%s] hw_done timed out\n",
-				  conn->base.id, conn->name);
-
-		/* Currently no support for overwriting flips, hence
-		 * stall for previous one to execute completely. */
-		ret = wait_for_completion_timeout(&commit->flip_done,
-						  10*HZ);
-		if (ret == 0)
-			DRM_ERROR("[CONNECTOR:%d:%s] flip_done timed out\n",
+		ret = drm_crtc_commit_wait(old_conn_state->commit);
+		if (ret)
+			DRM_ERROR("[CONNECTOR:%d:%s] commit wait timed out\n",
 				  conn->base.id, conn->name);
 	}
 
 	for_each_old_plane_in_state(old_state, plane, old_plane_state, i) {
-		commit = old_plane_state->commit;
-
-		if (!commit)
-			continue;
-
-		ret = wait_for_completion_timeout(&commit->hw_done,
-						  10*HZ);
-		if (ret == 0)
-			DRM_ERROR("[PLANE:%d:%s] hw_done timed out\n",
-				  plane->base.id, plane->name);
-
-		/* Currently no support for overwriting flips, hence
-		 * stall for previous one to execute completely. */
-		ret = wait_for_completion_timeout(&commit->flip_done,
-						  10*HZ);
-		if (ret == 0)
-			DRM_ERROR("[PLANE:%d:%s] flip_done timed out\n",
+		ret = drm_crtc_commit_wait(old_plane_state->commit);
+		if (ret)
+			DRM_ERROR("[PLANE:%d:%s] commit wait timed out\n",
 				  plane->base.id, plane->name);
 	}
 }

drivers/gpu/drm/vc4/vc4_kms.c

@@ -363,9 +363,8 @@ static void vc4_atomic_commit_tail(struct drm_atomic_state *state)
 	for_each_old_crtc_in_state(state, crtc, old_crtc_state, i) {
 		struct vc4_crtc_state *vc4_crtc_state =
 			to_vc4_crtc_state(old_crtc_state);
-		struct drm_crtc_commit *commit;
 		unsigned int channel = vc4_crtc_state->assigned_channel;
-		unsigned long done;
+		int ret;
 
 		if (channel == VC4_HVS_CHANNEL_DISABLED)
 			continue;
@@ -373,17 +372,9 @@ static void vc4_atomic_commit_tail(struct drm_atomic_state *state)
 		if (!old_hvs_state->fifo_state[channel].in_use)
 			continue;
 
-		commit = old_hvs_state->fifo_state[i].pending_commit;
-		if (!commit)
-			continue;
-
-		done = wait_for_completion_timeout(&commit->hw_done, 10 * HZ);
-		if (!done)
-			drm_err(dev, "Timed out waiting for hw_done\n");
-
-		done = wait_for_completion_timeout(&commit->flip_done, 10 * HZ);
-		if (!done)
-			drm_err(dev, "Timed out waiting for flip_done\n");
+		ret = drm_crtc_commit_wait(old_hvs_state->fifo_state[i].pending_commit);
+		if (ret)
+			drm_err(dev, "Timed out waiting for commit\n");
 	}
 
 	drm_atomic_helper_commit_modeset_disables(dev, state);

include/drm/drm_atomic.h

@@ -66,6 +66,8 @@
  *
  * For an implementation of how to use this look at
  * drm_atomic_helper_setup_commit() from the atomic helper library.
+ *
+ * See also drm_crtc_commit_wait().
  */
 struct drm_crtc_commit {
 	/**
@@ -436,6 +438,8 @@ static inline void drm_crtc_commit_put(struct drm_crtc_commit *commit)
 	kref_put(&commit->ref, __drm_crtc_commit_free);
 }
 
+int drm_crtc_commit_wait(struct drm_crtc_commit *commit);
+
 struct drm_atomic_state * __must_check
 drm_atomic_state_alloc(struct drm_device *dev);
 void drm_atomic_state_clear(struct drm_atomic_state *state);