drm/omap: add a comment why locking is missing

unpin_worker() calls omap_framebuffer_unpin() without any locks, which
looks very suspicious. However, both pin and unpin are always called via
the driver's private workqueue, so the access is synchronized that way.

Add a comment to make this clear.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

diff --git a/drivers/gpu/drm/omapdrm/omap_plane.c b/drivers/gpu/drm/omapdrm/omap_plane.c
index e03512c86bf891f250af18503622ce123990eded..6eedca107376ed3d8147ac18c0cd3696dfe1f276 100644 (file)
--- a/drivers/gpu/drm/omapdrm/omap_plane.c
+++ b/drivers/gpu/drm/omapdrm/omap_plane.c
@@ -71,6 +71,10 @@ static void omap_plane_unpin_worker(struct drm_flip_work *work, void *val)
                        container_of(work, struct omap_plane, unpin_work);
        struct drm_device *dev = omap_plane->base.dev;
 
+       /*
+        * omap_framebuffer_pin/unpin are always called from priv->wq,
+        * so there's no need for locking here.
+        */
        omap_framebuffer_unpin(val);
        mutex_lock(&dev->mode_config.mutex);
        drm_framebuffer_unreference(val);