drm/dp_helper: Mention the concurrency requirement hw_mutex

Drivers that allow concurrent access over multiple DP channels need to
provide additional locking, even though the hw_mutex field might
indicate otherwise. Clarify it in the documentation.

Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210616141529.630719-2-maxime@cerno.tech

diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 683aa98..9336bfb 100644 (file)
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -1913,6 +1913,10 @@ struct drm_dp_aux {
 
        /**
         * @hw_mutex: internal mutex used for locking transfers.
+        *
+        * Note that if the underlying hardware is shared among multiple
+        * channels, the driver needs to do additional locking to
+        * prevent concurrent access.
         */
        struct mutex hw_mutex;