drm/bridge: Add an ->atomic_check() hook

So that bridge drivers have a way to check/reject an atomic operation.
The drm_atomic_bridge_chain_check() (which is just a wrapper around
the ->atomic_check() hook) is called in place of
drm_bridge_chain_mode_fixup() (when ->atomic_check() is not implemented,
the core falls back on ->mode_fixup(), so the behavior should stay
the same for existing bridge drivers).

v10:
* Add changelog to the commit message

v8 -> v9:
* No changes

v7:
* Fix a NULL pointer dereference

v5 -> v6:
* No changes

v4:
* Add R-bs

v3:
* No changes

v2:
* Clarify the fact that ->atomic_check() is replacing ->mode_fixup()

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed by: Jernej Skrabec <jernej.skrabec@siol.net>
Tested-by: Jonas Karlman <jonas@kwiboo.se>
Link: https://patchwork.freedesktop.org/patch/msgid/20200128135514.108171-6-boris.brezillon@collabora.com

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index df76fe9..003c687 100644 (file)
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -437,12 +437,12 @@ mode_fixup(struct drm_atomic_state *state)
                funcs = encoder->helper_private;
 
                bridge = drm_bridge_chain_get_first_bridge(encoder);
-               ret = drm_bridge_chain_mode_fixup(bridge,
-                                       &new_crtc_state->mode,
-                                       &new_crtc_state->adjusted_mode);
-               if (!ret) {
-                       DRM_DEBUG_ATOMIC("Bridge fixup failed\n");
-                       return -EINVAL;
+               ret = drm_atomic_bridge_chain_check(bridge,
+                                                   new_crtc_state,
+                                                   new_conn_state);
+               if (ret) {
+                       DRM_DEBUG_ATOMIC("Bridge atomic check failed\n");
+                       return ret;
                }
 
                if (funcs && funcs->atomic_check) {

diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index f6206e6..c8beb13 100644 (file)
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -602,6 +602,72 @@ void drm_atomic_bridge_chain_enable(struct drm_bridge *bridge,
 }
 EXPORT_SYMBOL(drm_atomic_bridge_chain_enable);
 
+static int drm_atomic_bridge_check(struct drm_bridge *bridge,
+                                  struct drm_crtc_state *crtc_state,
+                                  struct drm_connector_state *conn_state)
+{
+       if (bridge->funcs->atomic_check) {
+               struct drm_bridge_state *bridge_state;
+               int ret;
+
+               bridge_state = drm_atomic_get_new_bridge_state(crtc_state->state,
+                                                              bridge);
+               if (WARN_ON(!bridge_state))
+                       return -EINVAL;
+
+               ret = bridge->funcs->atomic_check(bridge, bridge_state,
+                                                 crtc_state, conn_state);
+               if (ret)
+                       return ret;
+       } else if (bridge->funcs->mode_fixup) {
+               if (!bridge->funcs->mode_fixup(bridge, &crtc_state->mode,
+                                              &crtc_state->adjusted_mode))
+                       return -EINVAL;
+       }
+
+       return 0;
+}
+
+/**
+ * drm_atomic_bridge_chain_check() - Do an atomic check on the bridge chain
+ * @bridge: bridge control structure
+ * @crtc_state: new CRTC state
+ * @conn_state: new connector state
+ *
+ * Calls &drm_bridge_funcs.atomic_check() (falls back on
+ * &drm_bridge_funcs.mode_fixup()) op for all the bridges in the encoder chain,
+ * starting from the last bridge to the first. These are called before calling
+ * &drm_encoder_helper_funcs.atomic_check()
+ *
+ * RETURNS:
+ * 0 on success, a negative error code on failure
+ */
+int drm_atomic_bridge_chain_check(struct drm_bridge *bridge,
+                                 struct drm_crtc_state *crtc_state,
+                                 struct drm_connector_state *conn_state)
+{
+       struct drm_encoder *encoder;
+       struct drm_bridge *iter;
+
+       if (!bridge)
+               return 0;
+
+       encoder = bridge->encoder;
+       list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) {
+               int ret;
+
+               ret = drm_atomic_bridge_check(iter, crtc_state, conn_state);
+               if (ret)
+                       return ret;
+
+               if (iter == bridge)
+                       break;
+       }
+
+       return 0;
+}
+EXPORT_SYMBOL(drm_atomic_bridge_chain_check);
+
 #ifdef CONFIG_OF
 /**
  * of_drm_find_bridge - find the bridge corresponding to the device node in

diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
index df22f90..ff4df6e 100644 (file)
--- a/include/drm/drm_bridge.h
+++ b/include/drm/drm_bridge.h
@@ -111,7 +111,9 @@ struct drm_bridge_funcs {
         * this function passes all other callbacks must succeed for this
         * configuration.
         *
-        * The @mode_fixup callback is optional.
+        * The mode_fixup callback is optional. &drm_bridge_funcs.mode_fixup()
+        * is not called when &drm_bridge_funcs.atomic_check() is implemented,
+        * so only one of them should be provided.
         *
         * NOTE:
         *
@@ -369,6 +371,28 @@ struct drm_bridge_funcs {
                                     struct drm_bridge_state *state);
 
        /**
+        * @atomic_check:
+        *
+        * This method is responsible for checking bridge state correctness.
+        * It can also check the state of the surrounding components in chain
+        * to make sure the whole pipeline can work properly.
+        *
+        * &drm_bridge_funcs.atomic_check() hooks are called in reverse
+        * order (from the last to the first bridge).
+        *
+        * This method is optional. &drm_bridge_funcs.mode_fixup() is not
+        * called when &drm_bridge_funcs.atomic_check() is implemented, so only
+        * one of them should be provided.
+        *
+        * RETURNS:
+        * zero if the check passed, a negative error code otherwise.
+        */
+       int (*atomic_check)(struct drm_bridge *bridge,
+                           struct drm_bridge_state *bridge_state,
+                           struct drm_crtc_state *crtc_state,
+                           struct drm_connector_state *conn_state);
+
+       /**
         * @atomic_reset:
         *
         * Reset the bridge to a predefined state (or retrieve its current
@@ -542,6 +566,9 @@ void drm_bridge_chain_mode_set(struct drm_bridge *bridge,
 void drm_bridge_chain_pre_enable(struct drm_bridge *bridge);
 void drm_bridge_chain_enable(struct drm_bridge *bridge);
 
+int drm_atomic_bridge_chain_check(struct drm_bridge *bridge,
+                                 struct drm_crtc_state *crtc_state,
+                                 struct drm_connector_state *conn_state);
 void drm_atomic_bridge_chain_disable(struct drm_bridge *bridge,
                                     struct drm_atomic_state *state);
 void drm_atomic_bridge_chain_post_disable(struct drm_bridge *bridge,