drm/plane: check that fb_damage is set up when used

There's two stages of manual upload/invalidate displays:
- just handling dirtyfb and uploading the entire fb all the time
- looking at damage clips

In the latter case we support it through fbdev emulation (with
fb_defio), atomic property, and with the dirtfy clip rects.

Make sure at least the atomic property is set up as the main official
interface for this. Ideally we'd also check that
drm_atomic_helper_dirtyfb() is used and that fbdev defio is set up,
but that's quite a bit harder to do. Ideas very much welcome.

From a cursor audit drivers seem to be getting this right mostly, but
better to make sure. At least no one is bypassing the accessor
function.

v2:
- use drm_warn_once with a meaningful warning string (José)
- don't splat in the atomic check code for everyone (intel-gfx-ci)

Reviewed-by: José Roberto de Souza <jose.souza@intel.com> (v1)
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Cc: José Roberto de Souza <jose.souza@intel.com>
Cc: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210723083457.696939-2-daniel.vetter@ffwll.ch

drivers/gpu/drm/drm_atomic.c

@@ -659,7 +659,7 @@ static int drm_atomic_plane_check(const struct drm_plane_state *old_plane_state,
 		return -ENOSPC;
 	}
 
-	clips = drm_plane_get_damage_clips(new_plane_state);
+	clips = __drm_plane_get_damage_clips(new_plane_state);
 	num_clips = drm_plane_get_damage_clips_count(new_plane_state);
 
 	/* Make sure damage clips are valid and inside the fb. */

drivers/gpu/drm/drm_crtc_internal.h

@@ -260,6 +260,8 @@ int drm_plane_register_all(struct drm_device *dev);
 void drm_plane_unregister_all(struct drm_device *dev);
 int drm_plane_check_pixel_format(struct drm_plane *plane,
 				 u32 format, u64 modifier);
+struct drm_mode_rect *
+__drm_plane_get_damage_clips(const struct drm_plane_state *state);
 
 /* drm_bridge.c */
 void drm_bridge_detach(struct drm_bridge *bridge);

drivers/gpu/drm/drm_plane.c

@@ -1397,6 +1397,56 @@ int drm_mode_page_flip_ioctl(struct drm_device *dev,
 	return ret;
 }
 
+/**
+ * drm_plane_get_damage_clips_count - Returns damage clips count.
+ * @state: Plane state.
+ *
+ * Simple helper to get the number of &drm_mode_rect clips set by user-space
+ * during plane update.
+ *
+ * Return: Number of clips in plane fb_damage_clips blob property.
+ */
+unsigned int
+drm_plane_get_damage_clips_count(const struct drm_plane_state *state)
+{
+	return (state && state->fb_damage_clips) ?
+		state->fb_damage_clips->length/sizeof(struct drm_mode_rect) : 0;
+}
+EXPORT_SYMBOL(drm_plane_get_damage_clips_count);
+
+struct drm_mode_rect *
+__drm_plane_get_damage_clips(const struct drm_plane_state *state)
+{
+	return (struct drm_mode_rect *)((state && state->fb_damage_clips) ?
+					state->fb_damage_clips->data : NULL);
+}
+
+/**
+ * drm_plane_get_damage_clips - Returns damage clips.
+ * @state: Plane state.
+ *
+ * Note that this function returns uapi type &drm_mode_rect. Drivers might want
+ * to use the helper functions drm_atomic_helper_damage_iter_init() and
+ * drm_atomic_helper_damage_iter_next() or drm_atomic_helper_damage_merged() if
+ * the driver can only handle a single damage region at most.
+ *
+ * Return: Damage clips in plane fb_damage_clips blob property.
+ */
+struct drm_mode_rect *
+drm_plane_get_damage_clips(const struct drm_plane_state *state)
+{
+	struct drm_device *dev = state->plane->dev;
+	struct drm_mode_config *config = &dev->mode_config;
+
+	/* check that drm_plane_enable_fb_damage_clips() was called */
+	if (!drm_mode_obj_find_prop_id(&state->plane->base,
+				       config->prop_fb_damage_clips->base.id))
+		drm_warn_once(dev, "drm_plane_enable_fb_damage_clips() not called\n");
+
+	return __drm_plane_get_damage_clips(state);
+}
+EXPORT_SYMBOL(drm_plane_get_damage_clips);
+
 struct drm_property *
 drm_create_scaling_filter_prop(struct drm_device *dev,
 			       unsigned int supported_filters)

include/drm/drm_plane.h

@@ -897,39 +897,11 @@ static inline struct drm_plane *drm_plane_find(struct drm_device *dev,
 
 bool drm_any_plane_has_format(struct drm_device *dev,
 			      u32 format, u64 modifier);
-/**
- * drm_plane_get_damage_clips_count - Returns damage clips count.
- * @state: Plane state.
- *
- * Simple helper to get the number of &drm_mode_rect clips set by user-space
- * during plane update.
- *
- * Return: Number of clips in plane fb_damage_clips blob property.
- */
-static inline unsigned int
-drm_plane_get_damage_clips_count(const struct drm_plane_state *state)
-{
-	return (state && state->fb_damage_clips) ?
-		state->fb_damage_clips->length/sizeof(struct drm_mode_rect) : 0;
-}
+unsigned int
+drm_plane_get_damage_clips_count(const struct drm_plane_state *state);
 
-/**
- * drm_plane_get_damage_clips - Returns damage clips.
- * @state: Plane state.
- *
- * Note that this function returns uapi type &drm_mode_rect. Drivers might want
- * to use the helper functions drm_atomic_helper_damage_iter_init() and
- * drm_atomic_helper_damage_iter_next() or drm_atomic_helper_damage_merged() if
- * the driver can only handle a single damage region at most.
- *
- * Return: Damage clips in plane fb_damage_clips blob property.
- */
-static inline struct drm_mode_rect *
-drm_plane_get_damage_clips(const struct drm_plane_state *state)
-{
-	return (struct drm_mode_rect *)((state && state->fb_damage_clips) ?
-					state->fb_damage_clips->data : NULL);
-}
+struct drm_mode_rect *
+drm_plane_get_damage_clips(const struct drm_plane_state *state);
 
 int drm_plane_create_scaling_filter_property(struct drm_plane *plane,
 					     unsigned int supported_filters);