[PATCH] drm: Store the plane's index

[Chris Wilson]

Currently the plane's index is determined by walking the list of all
planes in the mode and finding the position of that plane in the list. A
linear walk, especially a linear walk within a linear walk as frequently
conceived by i915.ko [O(N^2)] quickly comes to dominate profiles.

The plane's index is constant for as long as no earlier planes are
removed from the list. For most drivers, planes are static, determined
at boot and then untouched until shutdown. Storing the index upon
construction and then only walking the tail upon removal should
be a major improvement for all.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Cc: Matt Roper <matthew.d.roper at intel.com>
---
 drivers/gpu/drm/drm_crtc.c | 38 +++++++++-----------------------------
 include/drm/drm_crtc.h     |  6 +++++-
 2 files changed, 14 insertions(+), 30 deletions(-)

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index 3a0384cce4a2..00ee01126b6f 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -1302,7 +1302,7 @@ int drm_universal_plane_init(struct drm_device *dev, struct drm_plane *plane,
 	plane->type = type;
 
 	list_add_tail(&plane->head, &config->plane_list);
-	config->num_total_plane++;
+	plane->index = config->num_total_plane++;
 	if (plane->type == DRM_PLANE_TYPE_OVERLAY)
 		config->num_overlay_plane++;
 
@@ -1369,6 +1369,7 @@ EXPORT_SYMBOL(drm_plane_init);
 void drm_plane_cleanup(struct drm_plane *plane)
 {
 	struct drm_device *dev = plane->dev;
+	struct drm_plane *other;
 
 	drm_modeset_lock_all(dev);
 	kfree(plane->format_types);
@@ -1376,6 +1377,10 @@ void drm_plane_cleanup(struct drm_plane *plane)
 
 	BUG_ON(list_empty(&plane->head));
 
+	other = list_next_entry(plane, head);
+	list_for_each_entry_from(other, &dev->mode_config.plane_list, head)
+		other->index--;
+
 	list_del(&plane->head);
 	dev->mode_config.num_total_plane--;
 	if (plane->type == DRM_PLANE_TYPE_OVERLAY)
@@ -1393,29 +1398,6 @@ void drm_plane_cleanup(struct drm_plane *plane)
 EXPORT_SYMBOL(drm_plane_cleanup);
 
 /**
- * drm_plane_index - find the index of a registered plane
- * @plane: plane to find index for
- *
- * Given a registered plane, return the index of that CRTC within a DRM
- * device's list of planes.
- */
-unsigned int drm_plane_index(struct drm_plane *plane)
-{
-	unsigned int index = 0;
-	struct drm_plane *tmp;
-
-	drm_for_each_plane(tmp, plane->dev) {
-		if (tmp == plane)
-			return index;
-
-		index++;
-	}
-
-	BUG();
-}
-EXPORT_SYMBOL(drm_plane_index);
-
-/**
  * drm_plane_from_index - find the registered plane at an index
  * @dev: DRM device
  * @idx: index of registered plane to find for
@@ -1427,13 +1409,11 @@ struct drm_plane *
 drm_plane_from_index(struct drm_device *dev, int idx)
 {
 	struct drm_plane *plane;
-	unsigned int i = 0;
 
-	drm_for_each_plane(plane, dev) {
-		if (i == idx)
+	drm_for_each_plane(plane, dev)
+		if (idx == plane->index)
 			return plane;
-		i++;
-	}
+
 	return NULL;
 }
 EXPORT_SYMBOL(drm_plane_from_index);
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 9771428e1ba8..eda3b1b3d3b4 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -1543,6 +1543,7 @@ struct drm_plane {
 	struct drm_object_properties properties;
 
 	enum drm_plane_type type;
+	unsigned index;
 
 	const struct drm_plane_helper_funcs *helper_private;
 
@@ -2316,7 +2317,10 @@ extern int drm_plane_init(struct drm_device *dev,
 			  const uint32_t *formats, unsigned int format_count,
 			  bool is_primary);
 extern void drm_plane_cleanup(struct drm_plane *plane);
-extern unsigned int drm_plane_index(struct drm_plane *plane);
+static inline unsigned int drm_plane_index(struct drm_plane *plane)
+{
+	return plane->index;
+}
 extern struct drm_plane * drm_plane_from_index(struct drm_device *dev, int idx);
 extern void drm_plane_force_disable(struct drm_plane *plane);
 extern int drm_plane_check_pixel_format(const struct drm_plane *plane,
-- 
2.8.1