[PATCH] drm: Don't prepare or cleanup unchanging frame buffers [v2]

[Keith Packard <keithp@keithp.com>]

When reconfiguring a plane position (as in moving the cursor), the
frame buffer for the cursor isn't changing, so don't call the prepare
or cleanup driver functions.

This avoids making cursor position updates block on all pending rendering.

v2: Track which planes have been prepared to know which to
    cleanup. Otherwise, failure paths and success paths would need
    different tests in the cleanup code as the plane state points to
    different places in the two cases.

cc: dri-devel@lists.freedesktop.org
cc: David Airlie <airlied@linux.ie>
Signed-off-by: Keith Packard <keithp@keithp.com>
---
 drivers/gpu/drm/drm_atomic_helper.c | 23 +++++++++++++----------
 include/drm/drm_crtc.h              |  1 +
 2 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index ddfa0d1..f7f3a51 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -1246,18 +1246,20 @@ EXPORT_SYMBOL(drm_atomic_helper_commit);
  * Returns:
  * 0 on success, negative error code on failure.
  */
+
 int drm_atomic_helper_prepare_planes(struct drm_device *dev,
 				     struct drm_atomic_state *state)
 {
-	int nplanes = dev->mode_config.num_total_plane;
+	struct drm_plane *plane;
+	struct drm_plane_state *plane_state;
 	int ret, i;
 
-	for (i = 0; i < nplanes; i++) {
+	for_each_plane_in_state(state, plane, plane_state, i) {
 		const struct drm_plane_helper_funcs *funcs;
-		struct drm_plane *plane = state->planes[i];
-		struct drm_plane_state *plane_state = state->plane_states[i];
 
-		if (!plane)
+		plane->prepared = false;
+
+		if (plane->state->fb == plane_state->fb)
 			continue;
 
 		funcs = plane->helper_private;
@@ -1267,24 +1269,22 @@ int drm_atomic_helper_prepare_planes(struct drm_device *dev,
 			if (ret)
 				goto fail;
 		}
+		plane->prepared = true;
 	}
 
 	return 0;
 
 fail:
-	for (i--; i >= 0; i--) {
+	for_each_plane_in_state(state, plane, plane_state, i) {
 		const struct drm_plane_helper_funcs *funcs;
-		struct drm_plane *plane = state->planes[i];
-		struct drm_plane_state *plane_state = state->plane_states[i];
 
-		if (!plane)
+		if (!plane->prepared)
 			continue;
 
 		funcs = plane->helper_private;
 
 		if (funcs->cleanup_fb)
 			funcs->cleanup_fb(plane, plane_state);
-
 	}
 
 	return ret;
@@ -1527,6 +1527,9 @@ void drm_atomic_helper_cleanup_planes(struct drm_device *dev,
 	for_each_plane_in_state(old_state, plane, plane_state, i) {
 		const struct drm_plane_helper_funcs *funcs;
 
+		if (!plane->prepared)
+			continue;
+
 		funcs = plane->helper_private;
 
 		if (funcs->cleanup_fb)
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index d1559cd..08b2033 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -1531,6 +1531,7 @@ struct drm_plane {
 	uint32_t *format_types;
 	unsigned int format_count;
 	bool format_default;
+	bool prepared;
 
 	struct drm_crtc *crtc;
 	struct drm_framebuffer *fb;
-- 
2.8.1