drm/atomic: integrate modeset lock with private objects

Follow the same pattern of locking as with other state objects. This
avoids boilerplate in the driver.
Signed-off-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20181022123122.30468-1-boris.brezillon@bootlin.com

drivers/gpu/drm/drm_atomic.c

@@ -676,6 +676,7 @@ static void drm_atomic_plane_print_state(struct drm_printer *p,
 
 /**
  * drm_atomic_private_obj_init - initialize private object
+ * @dev: DRM device this object will be attached to
  * @obj: private object
  * @state: initial private object state
  * @funcs: pointer to the struct of function pointers that identify the object
@@ -685,14 +686,18 @@ static void drm_atomic_plane_print_state(struct drm_printer *p,
  * driver private object that needs its own atomic state.
  */
 void
-drm_atomic_private_obj_init(struct drm_private_obj *obj,
+drm_atomic_private_obj_init(struct drm_device *dev,
+			    struct drm_private_obj *obj,
 			    struct drm_private_state *state,
 			    const struct drm_private_state_funcs *funcs)
 {
 	memset(obj, 0, sizeof(*obj));
 
+	drm_modeset_lock_init(&obj->lock);
+
 	obj->state = state;
 	obj->funcs = funcs;
+	list_add_tail(&obj->head, &dev->mode_config.privobj_list);
 }
 EXPORT_SYMBOL(drm_atomic_private_obj_init);
 
@@ -705,7 +710,9 @@ EXPORT_SYMBOL(drm_atomic_private_obj_init);
 void
 drm_atomic_private_obj_fini(struct drm_private_obj *obj)
 {
+	list_del(&obj->head);
 	obj->funcs->atomic_destroy_state(obj, obj->state);
+	drm_modeset_lock_fini(&obj->lock);
 }
 EXPORT_SYMBOL(drm_atomic_private_obj_fini);
 
@@ -715,8 +722,8 @@ EXPORT_SYMBOL(drm_atomic_private_obj_fini);
  * @obj: private object to get the state for
  *
  * This function returns the private object state for the given private object,
- * allocating the state if needed. It does not grab any locks as the caller is
- * expected to care of any required locking.
+ * allocating the state if needed. It will also grab the relevant private
+ * object lock to make sure that the state is consistent.
  *
  * RETURNS:
  *
@@ -726,7 +733,7 @@ struct drm_private_state *
 drm_atomic_get_private_obj_state(struct drm_atomic_state *state,
 				 struct drm_private_obj *obj)
 {
-	int index, num_objs, i;
+	int index, num_objs, i, ret;
 	size_t size;
 	struct __drm_private_objs_state *arr;
 	struct drm_private_state *obj_state;
@@ -735,6 +742,10 @@ drm_atomic_get_private_obj_state(struct drm_atomic_state *state,
 		if (obj == state->private_objs[i].ptr)
 			return state->private_objs[i].state;
 
+	ret = drm_modeset_lock(&obj->lock, state->acquire_ctx);
+	if (ret)
+		return ERR_PTR(ret);
+
 	num_objs = state->num_private_objs + 1;
 	size = sizeof(*state->private_objs) * num_objs;
 	arr = krealloc(state->private_objs, size, GFP_KERNEL);

drivers/gpu/drm/drm_dp_mst_topology.c

@@ -3221,7 +3221,7 @@ int drm_dp_mst_topology_mgr_init(struct drm_dp_mst_topology_mgr *mgr,
 	/* max. time slots - one slot for MTP header */
 	mst_state->avail_slots = 63;
 
-	drm_atomic_private_obj_init(&mgr->base,
+	drm_atomic_private_obj_init(dev, &mgr->base,
 				    &mst_state->base,
 				    &mst_state_funcs);
 

drivers/gpu/drm/drm_mode_config.c

@@ -381,6 +381,7 @@ void drm_mode_config_init(struct drm_device *dev)
 	INIT_LIST_HEAD(&dev->mode_config.property_list);
 	INIT_LIST_HEAD(&dev->mode_config.property_blob_list);
 	INIT_LIST_HEAD(&dev->mode_config.plane_list);
+	INIT_LIST_HEAD(&dev->mode_config.privobj_list);
 	idr_init(&dev->mode_config.crtc_idr);
 	idr_init(&dev->mode_config.tile_idr);
 	ida_init(&dev->mode_config.connector_ida);

drivers/gpu/drm/drm_modeset_lock.c

@@ -22,6 +22,7 @@
  */
 
 #include <drm/drmP.h>
+#include <drm/drm_atomic.h>
 #include <drm/drm_crtc.h>
 #include <drm/drm_modeset_lock.h>
 
@@ -394,6 +395,7 @@ EXPORT_SYMBOL(drm_modeset_unlock);
 int drm_modeset_lock_all_ctx(struct drm_device *dev,
 			     struct drm_modeset_acquire_ctx *ctx)
 {
+	struct drm_private_obj *privobj;
 	struct drm_crtc *crtc;
 	struct drm_plane *plane;
 	int ret;
@@ -414,6 +416,12 @@ int drm_modeset_lock_all_ctx(struct drm_device *dev,
 			return ret;
 	}
 
+	drm_for_each_privobj(privobj, dev) {
+		ret = drm_modeset_lock(&privobj->lock, ctx);
+		if (ret)
+			return ret;
+	}
+
 	return 0;
 }
 EXPORT_SYMBOL(drm_modeset_lock_all_ctx);

drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c

@@ -144,7 +144,7 @@ static int mdp5_global_obj_init(struct mdp5_kms *mdp5_kms)
 
 	state->mdp5_kms = mdp5_kms;
 
-	drm_atomic_private_obj_init(&mdp5_kms->glob_state,
+	drm_atomic_private_obj_init(mdp5_kms->dev, &mdp5_kms->glob_state,
 				    &state->base,
 				    &mdp5_global_state_funcs);
 	return 0;

drivers/gpu/drm/tegra/hub.c

@@ -716,7 +716,7 @@ static int tegra_display_hub_init(struct host1x_client *client)
 	if (!state)
 		return -ENOMEM;
 
-	drm_atomic_private_obj_init(&hub->base, &state->base,
+	drm_atomic_private_obj_init(drm, &hub->base, &state->base,
 				    &tegra_display_hub_state_funcs);
 
 	tegra->hub = hub;

drivers/gpu/drm/vc4/vc4_kms.c

@@ -432,7 +432,8 @@ int vc4_kms_load(struct drm_device *dev)
 	ctm_state = kzalloc(sizeof(*ctm_state), GFP_KERNEL);
 	if (!ctm_state)
 		return -ENOMEM;
-	drm_atomic_private_obj_init(&vc4->ctm_manager, &ctm_state->base,
+
+	drm_atomic_private_obj_init(dev, &vc4->ctm_manager, &ctm_state->base,
 				    &vc4_ctm_state_funcs);
 
 	drm_mode_config_reset(dev);

include/drm/drm_atomic.h

@@ -228,8 +228,30 @@ struct drm_private_state_funcs {
  * Currently only tracks the state update functions and the opaque driver
  * private state itself, but in the future might also track which
  * &drm_modeset_lock is required to duplicate and update this object's state.
+ *
+ * All private objects must be initialized before the DRM device they are
+ * attached to is registered to the DRM subsystem (call to drm_dev_register())
+ * and should stay around until this DRM device is unregistered (call to
+ * drm_dev_unregister()). In other words, private objects lifetime is tied
+ * to the DRM device lifetime. This implies that:
+ *
+ * 1/ all calls to drm_atomic_private_obj_init() must be done before calling
+ *    drm_dev_register()
+ * 2/ all calls to drm_atomic_private_obj_fini() must be done after calling
+ *    drm_dev_unregister()
  */
 struct drm_private_obj {
+	/**
+	 * @head: List entry used to attach a private object to a &drm_device
+	 * (queued to &drm_mode_config.privobj_list).
+	 */
+	struct list_head head;
+
+	/**
+	 * @lock: Modeset lock to protect the state object.
+	 */
+	struct drm_modeset_lock lock;
+
 	/**
 	 * @state: Current atomic state for this driver private object.
 	 */
@@ -244,6 +266,18 @@ struct drm_private_obj {
 	const struct drm_private_state_funcs *funcs;
 };
 
+/**
+ * drm_for_each_privobj() - private object iterator
+ *
+ * @privobj: pointer to the current private object. Updated after each
+ *	     iteration
+ * @dev: the DRM device we want get private objects from
+ *
+ * Allows one to iterate over all private objects attached to @dev
+ */
+#define drm_for_each_privobj(privobj, dev) \
+	list_for_each_entry(privobj, &(dev)->mode_config.privobj_list, head)
+
 /**
  * struct drm_private_state - base struct for driver private object state
  * @state: backpointer to global drm_atomic_state
@@ -400,7 +434,8 @@ struct drm_connector_state * __must_check
 drm_atomic_get_connector_state(struct drm_atomic_state *state,
 			       struct drm_connector *connector);
 
-void drm_atomic_private_obj_init(struct drm_private_obj *obj,
+void drm_atomic_private_obj_init(struct drm_device *dev,
+				 struct drm_private_obj *obj,
 				 struct drm_private_state *state,
 				 const struct drm_private_state_funcs *funcs);
 void drm_atomic_private_obj_fini(struct drm_private_obj *obj);

include/drm/drm_mode_config.h

@@ -512,6 +512,15 @@ struct drm_mode_config {
 	 */
 	struct list_head property_list;
 
+	/**
+	 * @privobj_list:
+	 *
+	 * List of private objects linked with &drm_private_obj.head. This is
+	 * invariant over the lifetime of a device and hence doesn't need any
+	 * locks.
+	 */
+	struct list_head privobj_list;
+
 	int min_width, min_height;
 	int max_width, max_height;
 	const struct drm_mode_config_funcs *funcs;