2 files changed, 74 insertions, 4 deletions

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index ff3c6eb5b6bd..8be9719284b0 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -459,10 +459,20 @@ mode_fixup(struct drm_atomic_state *state)
  *
  * Check the state object to see if the requested state is physically possible.
  * This does all the crtc and connector related computations for an atomic
- * update and adds any additional connectors needed for full modesets and calls
- * down into &drm_crtc_helper_funcs.mode_fixup and
- * &drm_encoder_helper_funcs.mode_fixup or
- * &drm_encoder_helper_funcs.atomic_check functions of the driver backend.
+ * update and adds any additional connectors needed for full modesets. It calls
+ * the various per-object callbacks in the follow order:
+ *
+ * 1. &drm_connector_helper_funcs.atomic_best_encoder for determining the new encoder.
+ * 2. &drm_connector_helper_funcs.atomic_check to validate the connector state.
+ * 3. If it's determined a modeset is needed then all connectors on the affected crtc
+ *    crtc are added and &drm_connector_helper_funcs.atomic_check is run on them.
+ * 4. &drm_bridge_funcs.mode_fixup is called on all encoder bridges.
+ * 5. &drm_encoder_helper_funcs.atomic_check is called to validate any encoder state.
+ *    This function is only called when the encoder will be part of a configured crtc,
+ *    it must not be used for implementing connector property validation.
+ *    If this function is NULL, &drm_atomic_encoder_helper_funcs.mode_fixup is called
+ *    instead.
+ * 6. &drm_crtc_helper_funcs.mode_fixup is called last, to fix up the mode with crtc constraints.
  *
  * &drm_crtc_state.mode_changed is set when the input mode is changed.
  * &drm_crtc_state.connectors_changed is set when a connector is added or
@@ -492,6 +502,7 @@ drm_atomic_helper_check_modeset(struct drm_device *dev,
         struct drm_connector *connector;
         struct drm_connector_state *old_connector_state, *new_connector_state;
         int i, ret;
+        unsigned connectors_mask = 0;
 
         for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state, new_crtc_state, i) {
                 bool has_connectors =
@@ -538,6 +549,8 @@ drm_atomic_helper_check_modeset(struct drm_device *dev,
                 return ret;
 
         for_each_oldnew_connector_in_state(state, connector, old_connector_state, new_connector_state, i) {
+                const struct drm_connector_helper_funcs *funcs = connector->helper_private;
+
                 /*
                  * This only sets crtc->connectors_changed for routing changes,
                  * drivers must set crtc->connectors_changed themselves when
@@ -555,6 +568,13 @@ drm_atomic_helper_check_modeset(struct drm_device *dev,
                             new_connector_state->link_status)
                                 new_crtc_state->connectors_changed = true;
                 }
+
+                if (funcs->atomic_check)
+                        ret = funcs->atomic_check(connector, new_connector_state);
+                if (ret)
+                        return ret;
+
+                connectors_mask += BIT(i);
         }
 
         /*
@@ -581,6 +601,22 @@ drm_atomic_helper_check_modeset(struct drm_device *dev,
                         return ret;
         }
 
+        /*
+         * Iterate over all connectors again, to make sure atomic_check()
+         * has been called on them when a modeset is forced.
+         */
+        for_each_oldnew_connector_in_state(state, connector, old_connector_state, new_connector_state, i) {
+                const struct drm_connector_helper_funcs *funcs = connector->helper_private;
+
+                if (connectors_mask & BIT(i))
+                        continue;
+
+                if (funcs->atomic_check)
+                        ret = funcs->atomic_check(connector, new_connector_state);
+                if (ret)
+                        return ret;
+        }
+
         return mode_fixup(state);
 }
 EXPORT_SYMBOL(drm_atomic_helper_check_modeset);
diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h
index 7847babd893c..c01c328f6cc8 100644
--- a/include/drm/drm_modeset_helper_vtables.h
+++ b/include/drm/drm_modeset_helper_vtables.h
@@ -872,6 +872,40 @@ struct drm_connector_helper_funcs {
          */
         struct drm_encoder *(*atomic_best_encoder)(struct drm_connector *connector,
                                                    struct drm_connector_state *connector_state);
+
+        /**
+         * @atomic_check:
+         *
+         * This hook is used to validate connector state. This function is
+         * called from &drm_atomic_helper_check_modeset, and is called when
+         * a connector property is set, or a modeset on the crtc is forced.
+         *
+         * Because &drm_atomic_helper_check_modeset may be called multiple times,
+         * this function should handle being called multiple times as well.
+         *
+         * This function is also allowed to inspect any other object's state and
+         * can add more state objects to the atomic commit if needed. Care must
+         * be taken though to ensure that state check and compute functions for
+         * these added states are all called, and derived state in other objects
+         * all updated. Again the recommendation is to just call check helpers
+         * until a maximal configuration is reached.
+         *
+         * NOTE:
+         *
+         * This function is called in the check phase of an atomic update. The
+         * driver is not allowed to change anything outside of the free-standing
+         * state objects passed-in or assembled in the overall &drm_atomic_state
+         * update tracking structure.
+         *
+         * RETURNS:
+         *
+         * 0 on success, -EINVAL if the state or the transition can't be
+         * supported, -ENOMEM on memory allocation failure and -EDEADLK if an
+         * attempt to obtain another state object ran into a &drm_modeset_lock
+         * deadlock.
+         */
+        int (*atomic_check)(struct drm_connector *connector,
+                            struct drm_connector_state *state);
 };
 
 /**