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>

1 files changed, 4 insertions, 0 deletions

diff --git a/drivers/gpu/drm/omapdrm/omap_plane.c b/drivers/gpu/drm/omapdrm/omap_plane.c
index e03512c86bf8..6eedca107376 100644
--- 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);