drm/bridge: Add a drm_bridge_state object

One of the last remaining objects to not have its atomic state.

This is being motivated by our attempt to support runtime bus-format
negotiation between elements of the bridge chain.
This patch just paves the road for such a feature by adding a new
drm_bridge_state object inheriting from drm_private_obj so we can
re-use some of the existing state initialization/tracking logic.

v10:
* Add changelog to the commit message

v9:
* Clarify the fact that the bridge->atomic_reset() and
  {connector,plane,crtc,...}->reset() semantics are different
* Move the drm_atomic_private_obj_init() call back to
  drm_bridge_attach()
* Check the presence of ->atomic_duplicate_state instead of
  ->atomic_reset in drm_atomic_add_encoder_bridges()
* Fix copy&paste errors in the atomic bridge state helpers doc
* Add A-b/R-b tags

v8:
* Move bridge state helpers out of the CONFIG_DEBUGFS section

v7:
* Move helpers, struct-defs, ... to atomic helper files to avoid the
  drm -> drm_kms_helper -> drm circular dep
* Stop providing default implementation for atomic state reset,
  duplicate and destroy hooks (has to do with the helper/core split)
* Drop all R-b/T-b as helpers have now be moved to other places

v6:
* Made helpers private, removed doc and moved them to satisfy dependencies
* Renamed helpers to _default_

v5:
* Re-introduced the helpers from v4

v4:
* Fix the doc
* Kill default helpers (inlined)
* Fix drm_atomic_get_bridge_state() to check for an ERR_PTR()
* Add Neil's R-b

v3:
* No changes

v2:
* Use drm_for_each_bridge_in_chain()
* Rename helpers to be more consistent with the rest of the DRM API
* Improve/fix the doc

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200128135514.108171-2-boris.brezillon@collabora.com

drivers/gpu/drm/drm_atomic.c

@@ -30,6 +30,7 @@
 
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_uapi.h>
+#include <drm/drm_bridge.h>
 #include <drm/drm_debugfs.h>
 #include <drm/drm_device.h>
 #include <drm/drm_drv.h>
@@ -1017,6 +1018,121 @@ static void drm_atomic_connector_print_state(struct drm_printer *p,
 		connector->funcs->atomic_print_state(p, state);
 }
 
+/**
+ * drm_atomic_get_bridge_state - get bridge state
+ * @state: global atomic state object
+ * @bridge: bridge to get state object for
+ *
+ * This function returns the bridge state for the given bridge, allocating it
+ * if needed. It will also grab the relevant bridge lock to make sure that the
+ * state is consistent.
+ *
+ * Returns:
+ *
+ * Either the allocated state or the error code encoded into the pointer. When
+ * the error is EDEADLK then the w/w mutex code has detected a deadlock and the
+ * entire atomic sequence must be restarted.
+ */
+struct drm_bridge_state *
+drm_atomic_get_bridge_state(struct drm_atomic_state *state,
+			    struct drm_bridge *bridge)
+{
+	struct drm_private_state *obj_state;
+
+	obj_state = drm_atomic_get_private_obj_state(state, &bridge->base);
+	if (IS_ERR(obj_state))
+		return ERR_CAST(obj_state);
+
+	return drm_priv_to_bridge_state(obj_state);
+}
+EXPORT_SYMBOL(drm_atomic_get_bridge_state);
+
+/**
+ * drm_atomic_get_old_bridge_state - get old bridge state, if it exists
+ * @state: global atomic state object
+ * @bridge: bridge to grab
+ *
+ * This function returns the old bridge state for the given bridge, or NULL if
+ * the bridge is not part of the global atomic state.
+ */
+struct drm_bridge_state *
+drm_atomic_get_old_bridge_state(struct drm_atomic_state *state,
+				struct drm_bridge *bridge)
+{
+	struct drm_private_state *obj_state;
+
+	obj_state = drm_atomic_get_old_private_obj_state(state, &bridge->base);
+	if (!obj_state)
+		return NULL;
+
+	return drm_priv_to_bridge_state(obj_state);
+}
+EXPORT_SYMBOL(drm_atomic_get_old_bridge_state);
+
+/**
+ * drm_atomic_get_new_bridge_state - get new bridge state, if it exists
+ * @state: global atomic state object
+ * @bridge: bridge to grab
+ *
+ * This function returns the new bridge state for the given bridge, or NULL if
+ * the bridge is not part of the global atomic state.
+ */
+struct drm_bridge_state *
+drm_atomic_get_new_bridge_state(struct drm_atomic_state *state,
+				struct drm_bridge *bridge)
+{
+	struct drm_private_state *obj_state;
+
+	obj_state = drm_atomic_get_new_private_obj_state(state, &bridge->base);
+	if (!obj_state)
+		return NULL;
+
+	return drm_priv_to_bridge_state(obj_state);
+}
+EXPORT_SYMBOL(drm_atomic_get_new_bridge_state);
+
+/**
+ * drm_atomic_add_encoder_bridges - add bridges attached to an encoder
+ * @state: atomic state
+ * @encoder: DRM encoder
+ *
+ * This function adds all bridges attached to @encoder. This is needed to add
+ * bridge states to @state and make them available when
+ * &bridge_funcs.atomic_{check,pre_enable,enable,disable_post_disable}() are
+ * called
+ *
+ * Returns:
+ * 0 on success or can fail with -EDEADLK or -ENOMEM. When the error is EDEADLK
+ * then the w/w mutex code has detected a deadlock and the entire atomic
+ * sequence must be restarted. All other errors are fatal.
+ */
+int
+drm_atomic_add_encoder_bridges(struct drm_atomic_state *state,
+			       struct drm_encoder *encoder)
+{
+	struct drm_bridge_state *bridge_state;
+	struct drm_bridge *bridge;
+
+	if (!encoder)
+		return 0;
+
+	DRM_DEBUG_ATOMIC("Adding all bridges for [encoder:%d:%s] to %p\n",
+			 encoder->base.id, encoder->name, state);
+
+	drm_for_each_bridge_in_chain(encoder, bridge) {
+		/* Skip bridges that don't implement the atomic state hooks. */
+		if (!bridge->funcs->atomic_duplicate_state)
+			continue;
+
+		bridge_state = drm_atomic_get_bridge_state(state, bridge);
+		if (IS_ERR(bridge_state))
+			return PTR_ERR(bridge_state);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_atomic_add_encoder_bridges);
+
 /**
  * drm_atomic_add_affected_connectors - add connectors for CRTC
  * @state: atomic state

drivers/gpu/drm/drm_atomic_helper.c

@@ -736,6 +736,26 @@ drm_atomic_helper_check_modeset(struct drm_device *dev,
 			return ret;
 	}
 
+	/*
+	 * Iterate over all connectors again, and add all affected bridges to
+	 * the state.
+	 */
+	for_each_oldnew_connector_in_state(state, connector,
+					   old_connector_state,
+					   new_connector_state, i) {
+		struct drm_encoder *encoder;
+
+		encoder = old_connector_state->best_encoder;
+		ret = drm_atomic_add_encoder_bridges(state, encoder);
+		if (ret)
+			return ret;
+
+		encoder = new_connector_state->best_encoder;
+		ret = drm_atomic_add_encoder_bridges(state, encoder);
+		if (ret)
+			return ret;
+	}
+
 	ret = mode_valid(state);
 	if (ret)
 		return ret;

drivers/gpu/drm/drm_atomic_state_helper.c

@@ -26,6 +26,7 @@
 
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_state_helper.h>
+#include <drm/drm_bridge.h>
 #include <drm/drm_connector.h>
 #include <drm/drm_crtc.h>
 #include <drm/drm_device.h>
@@ -551,3 +552,105 @@ void __drm_atomic_helper_private_obj_duplicate_state(struct drm_private_obj *obj
 	memcpy(state, obj->state, sizeof(*state));
 }
 EXPORT_SYMBOL(__drm_atomic_helper_private_obj_duplicate_state);
+
+/**
+ * __drm_atomic_helper_bridge_duplicate_state() - Copy atomic bridge state
+ * @bridge: bridge object
+ * @state: atomic bridge state
+ *
+ * Copies atomic state from a bridge's current state and resets inferred values.
+ * This is useful for drivers that subclass the bridge state.
+ */
+void __drm_atomic_helper_bridge_duplicate_state(struct drm_bridge *bridge,
+						struct drm_bridge_state *state)
+{
+	__drm_atomic_helper_private_obj_duplicate_state(&bridge->base,
+							&state->base);
+	state->bridge = bridge;
+}
+EXPORT_SYMBOL(__drm_atomic_helper_bridge_duplicate_state);
+
+/**
+ * drm_atomic_helper_bridge_duplicate_state() - Duplicate a bridge state object
+ * @bridge: bridge object
+ *
+ * Allocates a new bridge state and initializes it with the current bridge
+ * state values. This helper is meant to be used as a bridge
+ * &drm_bridge_funcs.atomic_duplicate_state hook for bridges that don't
+ * subclass the bridge state.
+ */
+struct drm_bridge_state *
+drm_atomic_helper_bridge_duplicate_state(struct drm_bridge *bridge)
+{
+	struct drm_bridge_state *new;
+
+	if (WARN_ON(!bridge->base.state))
+		return NULL;
+
+	new = kzalloc(sizeof(*new), GFP_KERNEL);
+	if (new)
+		__drm_atomic_helper_bridge_duplicate_state(bridge, new);
+
+	return new;
+}
+EXPORT_SYMBOL(drm_atomic_helper_bridge_duplicate_state);
+
+/**
+ * drm_atomic_helper_bridge_destroy_state() - Destroy a bridge state object
+ * @bridge: the bridge this state refers to
+ * @state: bridge state to destroy
+ *
+ * Destroys a bridge state previously created by
+ * &drm_atomic_helper_bridge_reset() or
+ * &drm_atomic_helper_bridge_duplicate_state(). This helper is meant to be
+ * used as a bridge &drm_bridge_funcs.atomic_destroy_state hook for bridges
+ * that don't subclass the bridge state.
+ */
+void drm_atomic_helper_bridge_destroy_state(struct drm_bridge *bridge,
+					    struct drm_bridge_state *state)
+{
+	kfree(state);
+}
+EXPORT_SYMBOL(drm_atomic_helper_bridge_destroy_state);
+
+/**
+ * __drm_atomic_helper_bridge_reset() - Initialize a bridge state to its
+ *					default
+ * @bridge: the bridge this state refers to
+ * @state: bridge state to initialize
+ *
+ * Initializes the bridge state to default values. This is meant to be called
+ * by the bridge &drm_bridge_funcs.atomic_reset hook for bridges that subclass
+ * the bridge state.
+ */
+void __drm_atomic_helper_bridge_reset(struct drm_bridge *bridge,
+				      struct drm_bridge_state *state)
+{
+	memset(state, 0, sizeof(*state));
+	state->bridge = bridge;
+}
+EXPORT_SYMBOL(__drm_atomic_helper_bridge_reset);
+
+/**
+ * drm_atomic_helper_bridge_reset() - Allocate and initialize a bridge state
+ *				      to its default
+ * @bridge: the bridge this state refers to
+ * @state: bridge state to initialize
+ *
+ * Allocates the bridge state and initializes it to default values. This helper
+ * is meant to be used as a bridge &drm_bridge_funcs.atomic_reset hook for
+ * bridges that don't subclass the bridge state.
+ */
+struct drm_bridge_state *
+drm_atomic_helper_bridge_reset(struct drm_bridge *bridge)
+{
+	struct drm_bridge_state *bridge_state;
+
+	bridge_state = kzalloc(sizeof(*bridge_state), GFP_KERNEL);
+	if (!bridge_state)
+		return ERR_PTR(-ENOMEM);
+
+	__drm_atomic_helper_bridge_reset(bridge, bridge_state);
+	return bridge_state;
+}
+EXPORT_SYMBOL(drm_atomic_helper_bridge_reset);

drivers/gpu/drm/drm_bridge.c

@@ -25,6 +25,7 @@
 #include <linux/module.h>
 #include <linux/mutex.h>
 
+#include <drm/drm_atomic_state_helper.h>
 #include <drm/drm_bridge.h>
 #include <drm/drm_encoder.h>
 
@@ -89,6 +90,31 @@ void drm_bridge_remove(struct drm_bridge *bridge)
 }
 EXPORT_SYMBOL(drm_bridge_remove);
 
+static struct drm_private_state *
+drm_bridge_atomic_duplicate_priv_state(struct drm_private_obj *obj)
+{
+	struct drm_bridge *bridge = drm_priv_to_bridge(obj);
+	struct drm_bridge_state *state;
+
+	state = bridge->funcs->atomic_duplicate_state(bridge);
+	return state ? &state->base : NULL;
+}
+
+static void
+drm_bridge_atomic_destroy_priv_state(struct drm_private_obj *obj,
+				     struct drm_private_state *s)
+{
+	struct drm_bridge_state *state = drm_priv_to_bridge_state(s);
+	struct drm_bridge *bridge = drm_priv_to_bridge(obj);
+
+	bridge->funcs->atomic_destroy_state(bridge, state);
+}
+
+static const struct drm_private_state_funcs drm_bridge_priv_state_funcs = {
+	.atomic_duplicate_state = drm_bridge_atomic_duplicate_priv_state,
+	.atomic_destroy_state = drm_bridge_atomic_destroy_priv_state,
+};
+
 /**
  * drm_bridge_attach - attach the bridge to an encoder's chain
  *
@@ -135,15 +161,35 @@ int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
 
 	if (bridge->funcs->attach) {
 		ret = bridge->funcs->attach(bridge);
-		if (ret < 0) {
-			list_del(&bridge->chain_node);
-			bridge->dev = NULL;
-			bridge->encoder = NULL;
-			return ret;
+		if (ret < 0)
+			goto err_reset_bridge;
+	}
+
+	if (bridge->funcs->atomic_reset) {
+		struct drm_bridge_state *state;
+
+		state = bridge->funcs->atomic_reset(bridge);
+		if (IS_ERR(state)) {
+			ret = PTR_ERR(state);
+			goto err_detach_bridge;
 		}
+
+		drm_atomic_private_obj_init(bridge->dev, &bridge->base,
+					    &state->base,
+					    &drm_bridge_priv_state_funcs);
 	}
 
 	return 0;
+
+err_detach_bridge:
+	if (bridge->funcs->detach)
+		bridge->funcs->detach(bridge);
+
+err_reset_bridge:
+	bridge->dev = NULL;
+	bridge->encoder = NULL;
+	list_del(&bridge->chain_node);
+	return ret;
 }
 EXPORT_SYMBOL(drm_bridge_attach);
 
@@ -155,6 +201,9 @@ void drm_bridge_detach(struct drm_bridge *bridge)
 	if (WARN_ON(!bridge->dev))
 		return;
 
+	if (bridge->funcs->atomic_reset)
+		drm_atomic_private_obj_fini(&bridge->base);
+
 	if (bridge->funcs->detach)
 		bridge->funcs->detach(bridge);
 

include/drm/drm_atomic.h

@@ -669,6 +669,9 @@ __drm_atomic_get_current_plane_state(struct drm_atomic_state *state,
 	return plane->state;
 }
 
+int __must_check
+drm_atomic_add_encoder_bridges(struct drm_atomic_state *state,
+			       struct drm_encoder *encoder);
 int __must_check
 drm_atomic_add_affected_connectors(struct drm_atomic_state *state,
 				   struct drm_crtc *crtc);
@@ -992,4 +995,35 @@ drm_atomic_crtc_effectively_active(const struct drm_crtc_state *state)
 	return state->active || state->self_refresh_active;
 }
 
+/**
+ * struct drm_bridge_state - Atomic bridge state object
+ */
+struct drm_bridge_state {
+	/**
+	 * @base: inherit from &drm_private_state
+	 */
+	struct drm_private_state base;
+
+	/**
+	 * @bridge: the bridge this state refers to
+	 */
+	struct drm_bridge *bridge;
+};
+
+static inline struct drm_bridge_state *
+drm_priv_to_bridge_state(struct drm_private_state *priv)
+{
+	return container_of(priv, struct drm_bridge_state, base);
+}
+
+struct drm_bridge_state *
+drm_atomic_get_bridge_state(struct drm_atomic_state *state,
+			    struct drm_bridge *bridge);
+struct drm_bridge_state *
+drm_atomic_get_old_bridge_state(struct drm_atomic_state *state,
+				struct drm_bridge *bridge);
+struct drm_bridge_state *
+drm_atomic_get_new_bridge_state(struct drm_atomic_state *state,
+				struct drm_bridge *bridge);
+
 #endif /* DRM_ATOMIC_H_ */

include/drm/drm_atomic_state_helper.h

@@ -26,6 +26,8 @@
 
 #include <linux/types.h>
 
+struct drm_bridge;
+struct drm_bridge_state;
 struct drm_crtc;
 struct drm_crtc_state;
 struct drm_plane;
@@ -80,3 +82,14 @@ void drm_atomic_helper_connector_destroy_state(struct drm_connector *connector,
 					  struct drm_connector_state *state);
 void __drm_atomic_helper_private_obj_duplicate_state(struct drm_private_obj *obj,
 						     struct drm_private_state *state);
+
+void __drm_atomic_helper_bridge_duplicate_state(struct drm_bridge *bridge,
+						struct drm_bridge_state *state);
+struct drm_bridge_state *
+drm_atomic_helper_bridge_duplicate_state(struct drm_bridge *bridge);
+void drm_atomic_helper_bridge_destroy_state(struct drm_bridge *bridge,
+					    struct drm_bridge_state *state);
+void __drm_atomic_helper_bridge_reset(struct drm_bridge *bridge,
+				      struct drm_bridge_state *state);
+struct drm_bridge_state *
+drm_atomic_helper_bridge_reset(struct drm_bridge *bridge);

include/drm/drm_bridge.h

@@ -25,6 +25,8 @@
 
 #include <linux/list.h>
 #include <linux/ctype.h>
+
+#include <drm/drm_atomic.h>
 #include <drm/drm_encoder.h>
 #include <drm/drm_mode_object.h>
 #include <drm/drm_modes.h>
@@ -338,6 +340,56 @@ struct drm_bridge_funcs {
 	 */
 	void (*atomic_post_disable)(struct drm_bridge *bridge,
 				    struct drm_atomic_state *old_state);
+
+	/**
+	 * @atomic_duplicate_state:
+	 *
+	 * Duplicate the current bridge state object (which is guaranteed to be
+	 * non-NULL).
+	 *
+	 * The atomic_duplicate_state() is optional. When not implemented the
+	 * core allocates a drm_bridge_state object and calls
+	 * &__drm_atomic_helper_bridge_duplicate_state() to initialize it.
+	 *
+	 * RETURNS:
+	 * A valid drm_bridge_state object or NULL if the allocation fails.
+	 */
+	struct drm_bridge_state *(*atomic_duplicate_state)(struct drm_bridge *bridge);
+
+	/**
+	 * @atomic_destroy_state:
+	 *
+	 * Destroy a bridge state object previously allocated by
+	 * &drm_bridge_funcs.atomic_duplicate_state().
+	 *
+	 * The atomic_destroy_state hook is optional. When not implemented the
+	 * core calls kfree() on the state.
+	 */
+	void (*atomic_destroy_state)(struct drm_bridge *bridge,
+				     struct drm_bridge_state *state);
+
+	/**
+	 * @atomic_reset:
+	 *
+	 * Reset the bridge to a predefined state (or retrieve its current
+	 * state) and return a &drm_bridge_state object matching this state.
+	 * This function is called at attach time.
+	 *
+	 * The atomic_reset hook is mandatory if the bridge implements any of
+	 * the atomic hooks, and should be left unassigned otherwise.
+	 *
+	 * Note that the atomic_reset() semantics is not exactly matching the
+	 * reset() semantics found on other components (connector, plane, ...).
+	 * 1/ The reset operation happens when the bridge is attached, not when
+	 *    drm_mode_config_reset() is called
+	 * 2/ It's meant to be used exclusively on bridges that have been
+	 *    converted to the ATOMIC API
+	 *
+	 * RETURNS:
+	 * A valid drm_bridge_state object in case of success, an ERR_PTR()
+	 * giving the reason of the failure otherwise.
+	 */
+	struct drm_bridge_state *(*atomic_reset)(struct drm_bridge *bridge);
 };
 
 /**
@@ -380,6 +432,8 @@ struct drm_bridge_timings {
  * struct drm_bridge - central DRM bridge control structure
  */
 struct drm_bridge {
+	/** @base: inherit from &drm_private_object */
+	struct drm_private_obj base;
 	/** @dev: DRM device this bridge belongs to */
 	struct drm_device *dev;
 	/** @encoder: encoder to which this bridge is connected */
@@ -404,6 +458,12 @@ struct drm_bridge {
 	void *driver_private;
 };
 
+static inline struct drm_bridge *
+drm_priv_to_bridge(struct drm_private_obj *priv)
+{
+	return container_of(priv, struct drm_bridge, base);
+}
+
 void drm_bridge_add(struct drm_bridge *bridge);
 void drm_bridge_remove(struct drm_bridge *bridge);
 struct drm_bridge *of_drm_find_bridge(struct device_node *np);