Re: [PATCH v3 09/21] drm/bridge: Add a drm_bridge_state object

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Boris,

Thank you for the patch.

On Wed, Oct 23, 2019 at 05:45:00PM +0200, Boris Brezillon wrote:
> 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.
> 
> Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
> ---
> Changes in v3:
> * None
> 
> Changes in 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
> ---
>  drivers/gpu/drm/drm_atomic.c        |  39 +++++++
>  drivers/gpu/drm/drm_atomic_helper.c |  20 ++++
>  drivers/gpu/drm/drm_bridge.c        | 168 +++++++++++++++++++++++++++-
>  include/drm/drm_atomic.h            |   3 +
>  include/drm/drm_bridge.h            | 118 +++++++++++++++++++
>  5 files changed, 343 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index 419381abbdd1..6c249ce39380 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/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>
> @@ -1010,6 +1011,44 @@ static void drm_atomic_connector_print_state(struct drm_printer *p,
>  		connector->funcs->atomic_print_state(p, 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) {
> +		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
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index f02ddffd4960..de985ba7ce2d 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -730,6 +730,26 @@ 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;
> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> index c5cf8a9c4237..c53966767782 100644
> --- a/drivers/gpu/drm/drm_bridge.c
> +++ b/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 +90,38 @@ 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;
> +
> +	if (bridge->funcs->atomic_duplicate_state)
> +		state = bridge->funcs->atomic_duplicate_state(bridge);
> +	else
> +		state = drm_atomic_helper_bridge_duplicate_state(bridge);
> +
> +	return &state->base;
> +}
> +
> +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);
> +
> +	if (bridge->funcs->atomic_destroy_state)
> +		bridge->funcs->atomic_destroy_state(bridge, state);
> +	else
> +		drm_atomic_helper_bridge_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
>   *
> @@ -114,6 +147,7 @@ EXPORT_SYMBOL(drm_bridge_remove);
>  int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
>  		      struct drm_bridge *previous)
>  {
> +	struct drm_bridge_state *state;
>  	LIST_HEAD(tmp_list);
>  	int ret;
>  
> @@ -132,19 +166,39 @@ int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
>  
>  	if (bridge->funcs->attach) {
>  		ret = bridge->funcs->attach(bridge);
> -		if (ret < 0) {
> -			bridge->dev = NULL;
> -			bridge->encoder = NULL;
> -			return ret;
> -		}
> +		if (ret < 0)
> +			goto err_reset_bridge;
>  	}
>  
> +	if (bridge->funcs->atomic_reset)
> +		state = bridge->funcs->atomic_reset(bridge);
> +	else
> +		state = drm_atomic_helper_bridge_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);
> +
>  	if (previous)
>  		list_splice(&tmp_list, &previous->chain_node);
>  	else
>  		list_splice(&tmp_list, &encoder->bridge_chain);
>  
>  	return 0;
> +
> +err_detach_bridge:
> +	if (bridge->funcs->detach)
> +		bridge->funcs->detach(bridge);
> +
> +err_reset_bridge:
> +	bridge->dev = NULL;
> +	bridge->encoder = NULL;
> +	return ret;
>  }
>  EXPORT_SYMBOL(drm_bridge_attach);
>  
> @@ -156,6 +210,8 @@ void drm_bridge_detach(struct drm_bridge *bridge)
>  	if (WARN_ON(!bridge->dev))
>  		return;
>  
> +	drm_atomic_private_obj_fini(&bridge->base);
> +
>  	if (bridge->funcs->detach)
>  		bridge->funcs->detach(bridge);
>  
> @@ -522,6 +578,108 @@ void drm_atomic_bridge_chain_enable(struct drm_bridge *bridge,
>  }
>  EXPORT_SYMBOL(drm_atomic_bridge_chain_enable);
>  
> +/**
> + * drm_atomic_helper_bridge_destroy_state() - Default destroy state helper
> + * @bridge: the bridge this state refers to
> + * @state: state object to destroy
> + *
> + * Just a simple kfree() for now.
> + */
> +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);

As this function is called as the default in
+drm_bridge_atomic_destroy_priv_state(), does it need to be exported ?

> +
> +/**
> + * __drm_atomic_helper_bridge_reset() - Initialize a bridge state to its
> + *					default
> + * @bridge: the bridge this state is refers to

s/is refers/refers/

> + * @state: bridge state to initialize
> + *
> + * For now it's just a memset(0) plus a state->bridge assignment. Might
> + * be extended in the future.

"Might" is an understatement :-) This function will be extended when the
drm_bridge_state structure will gain new fields that need to be
initialized. I would have dropped this paragraph, up to you. You could
maybe replace it with

"Initialize the bridge state to default values. This is meant to be
called by the bridge &drm_plane_funcs.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() - default &drm_plane_funcs.reset hook for
> + *				      bridges
> + * @bridge: the bridge to reset state on
> + *
> + * Resets the atomic state for @bridge by freeing the state pointer (which
> + * might be NULL, e.g. at driver load time) and allocating a new empty state
> + * object.

The function doesn't free the state pointer...

> + *
> + * RETURNS:
> + * A valid drm_bridge_state object in case of success, an ERR_PTR()
> + * giving the reaon of the failure otherwise.

s/reaon/reason/

> + */
> +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);
> +
> +/**
> + * __drm_atomic_helper_bridge_duplicate_state() - Copy the content of the
> + *						  current bridge state into a
> + *						  new one

Maybe "Copy atomic bridge state" to match the other helpers ?

> + * @bridge: bridge element the old and new states are referring to
> + * @new: new bridge state to copy to
> + *
> + * Should be used by custom &drm_bridge_funcs.atomic_duplicate() implementation
> + * to copy the previous state into the new object.

The documentation of these helpers seems to differ from the other atomic
state helpers. Shouldn't they be consistent ?

> + */
> +void __drm_atomic_helper_bridge_duplicate_state(struct drm_bridge *bridge,
> +						struct drm_bridge_state *new)
> +{
> +	__drm_atomic_helper_private_obj_duplicate_state(&bridge->base,
> +							&new->base);
> +	new->bridge = bridge;
> +}
> +EXPORT_SYMBOL(__drm_atomic_helper_bridge_duplicate_state);
> +
> +/**
> + * drm_atomic_helper_duplicate_bridge_state() - Default duplicate state helper
> + * @bridge: bridge containing the state to duplicate
> + *
> + * Default implementation of &drm_bridge_funcs.atomic_duplicate().
> + *
> + * RETURNS:
> + * a valid state object or NULL if the allocation fails.
> + */
> +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);

As this function is called as the default in
drm_bridge_atomic_duplicate_priv_state(), does it need to be exported ?

> +
>  #ifdef CONFIG_OF
>  /**
>   * of_drm_find_bridge - find the bridge corresponding to the device node in
> diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
> index 927e1205d7aa..1c0a08217712 100644
> --- a/include/drm/drm_atomic.h
> +++ b/include/drm/drm_atomic.h
> @@ -660,6 +660,9 @@ __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);
> diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> index 238e84ab63a3..a608c47d1de5 100644
> --- a/include/drm/drm_bridge.h
> +++ b/include/drm/drm_bridge.h
> @@ -25,6 +25,7 @@
>  
>  #include <linux/list.h>
>  #include <linux/ctype.h>
> +#include <drm/drm_atomic.h>

While at it I'd add a blank line above.

>  #include <drm/drm_encoder.h>
>  #include <drm/drm_mode_object.h>
>  #include <drm/drm_modes.h>
> @@ -33,6 +34,23 @@ struct drm_bridge;
>  struct drm_bridge_timings;
>  struct drm_panel;
>  
> +/**
> + * struct drm_bridge_state - Atomic bridge state object
> + * @base: inherit from &drm_private_state
> + * @bridge: the bridge this state refers to
> + */
> +struct drm_bridge_state {
> +	struct drm_private_state base;
> +
> +	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_funcs - drm_bridge control functions
>   */
> @@ -338,6 +356,48 @@ struct drm_bridge_funcs {
>  	 */
>  	void (*atomic_post_disable)(struct drm_bridge *bridge,
>  				    struct drm_atomic_state *state);
> +
> +	/**
> +	 * @atomic_duplicate_state:
> +	 *
> +	 * Duplicate the current bridge state object (which is guaranteed to be
> +	 * non-NULL).
> +	 *
> +	 * The atomic_duplicate_state() is optional, the core falls back on
> +	 * &drm_atomic_helper_bridge_duplicate_state() when not implemented.
> +	 *
> +	 * 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, the coref falls back on

s/coref/core/

> +	 * &drm_atomic_helper_bridge_destroy_state() when not implemented.
> +	 */
> +	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 optional, the core falls back on
> +	 * &drm_atomic_helper_bridge_reset() when not implemented.
> +	 *
> +	 * RETURNS:
> +	 * A valid drm_bridge_state object in case of success, an ERR_PTR()
> +	 * giving the reaon of the failure otherwise.

s/reaon/reason/

> +	 */
> +	struct drm_bridge_state *(*atomic_reset)(struct drm_bridge *bridge);
>  };
>  
>  /**
> @@ -380,6 +440,8 @@ 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 +466,12 @@ 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);
> @@ -475,6 +543,56 @@ void drm_atomic_bridge_chain_pre_enable(struct drm_bridge *bridge,
>  void drm_atomic_bridge_chain_enable(struct drm_bridge *bridge,
>  				    struct drm_atomic_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);
> +void drm_atomic_helper_bridge_destroy_state(struct drm_bridge *bridge,
> +					    struct drm_bridge_state *state);
> +void __drm_atomic_helper_bridge_duplicate_state(struct drm_bridge *bridge,
> +						struct drm_bridge_state *new);
> +struct drm_bridge_state *
> +drm_atomic_helper_bridge_duplicate_state(struct drm_bridge *bridge);
> +
> +static inline 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 (!obj_state)
> +		return NULL;
> +
> +	return drm_priv_to_bridge_state(obj_state);
> +}
> +
> +static inline 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);
> +}
> +
> +static inline 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);
> +}
> +
>  #ifdef CONFIG_DRM_PANEL_BRIDGE
>  struct drm_bridge *drm_panel_bridge_add(struct drm_panel *panel);
>  struct drm_bridge *drm_panel_bridge_add_typed(struct drm_panel *panel,

-- 
Regards,

Laurent Pinchart
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