[v4,08/11] drm/bridge: Add a drm_bridge_state object

Commit Message

Boris Brezillon Dec. 3, 2019, 2:15 p.m. UTC

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 <[e-mail]>
Reviewed-by: Neil Armstrong <[e-mail]>
---
Changes in 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

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        | 118 ++++++++++++++++++++++++++--
 include/drm/drm_atomic.h            |   3 +
 include/drm/drm_bridge.h            | 116 +++++++++++++++++++++++++++
 5 files changed, 290 insertions(+), 6 deletions(-)

Comments

Laurent Pinchart Dec. 3, 2019, 6:17 p.m. UTC | #1

Hi Boris,

Thank you for the patch.

On Tue, Dec 03, 2019 at 03:15:12PM +0100, 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 <[e-mail]>
> Reviewed-by: Neil Armstrong <[e-mail]>
> ---
> Changes in v4:
> * Fix the doc
> * Kill default helpers (inlined)

I liked the default helpers, inlining their content makes the code more
difficult to follow in my opinion. I will however not push back if you
prefer not to have them.

> * Fix drm_atomic_get_bridge_state() to check for an ERR_PTR()
> * Add Neil's R-b
> 
> 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        | 118 ++++++++++++++++++++++++++--
>  include/drm/drm_atomic.h            |   3 +
>  include/drm/drm_bridge.h            | 116 +++++++++++++++++++++++++++
>  5 files changed, 290 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index 14aeaf736321..02f8034f5240 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>
> @@ -1015,6 +1016,44 @@ 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 29c3115bf9e2..e2f7f336a2d2 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 b6517b4fa3d1..bf5a2243a115 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 +90,48 @@ 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);
> +
> +		return state ? &state->base : NULL;
> +	}
> +
> +	if (WARN_ON(!bridge->base.state))
> +		return NULL;
> +
> +	state = kzalloc(sizeof(*state), GFP_KERNEL);
> +	if (!state)
> +		return NULL;
> +
> +	__drm_atomic_helper_bridge_duplicate_state(bridge, state);
> +
> +	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
> +		kfree(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 +157,7 @@ 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;
>  	int ret;
>  
>  	if (!encoder || !bridge)
> @@ -135,15 +179,40 @@ 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) {
> +		state = bridge->funcs->atomic_reset(bridge);
> +	} else {
> +		state = kzalloc(sizeof(*state), GFP_KERNEL);
> +		if (state)
> +			__drm_atomic_helper_bridge_reset(bridge, state);
> +		else
> +			state = ERR_PTR(-ENOMEM);
> +	}
> +
> +	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 +224,8 @@ 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);
>  
> @@ -516,6 +587,41 @@ void drm_atomic_bridge_chain_enable(struct drm_bridge *bridge,
>  }
>  EXPORT_SYMBOL(drm_atomic_bridge_chain_enable);
>  
> +/**
> + * __drm_atomic_helper_bridge_reset() - Initialize a bridge state to its
> + *					default
> + * @bridge: the bridge this state is refers to
> + * @state: bridge state to initialize
> + *
> + * Initialize the bridge state to default values. This is meant to be* called

s/be\*/be/

Reviewed-by: Laurent Pinchart <[e-mail]>

> + * 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_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);
> +
>  #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 b6c73fd9f55a..e08582773d6c 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 d7d714023050..db5fc18d49bd 100644
> --- a/include/drm/drm_bridge.h
> +++ b/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>
> @@ -33,6 +35,23 @@ 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 +357,49 @@ 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 optional. When not implemented the core
> +	 * allocates a new state and calls &__drm_atomic_helper_bridge_reset().
> +	 *
> +	 * 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 +442,8 @@ 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 +468,12 @@ 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);
> @@ -491,6 +561,52 @@ 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_duplicate_state(struct drm_bridge *bridge,
> +						struct drm_bridge_state *new);
> +
> +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 (IS_ERR(obj_state))
> +		return ERR_CAST(obj_state);
> +
> +	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,
> -- 
> 2.23.0
>

Boris Brezillon Dec. 4, 2019, 9:03 a.m. UTC | #2

On Tue, 3 Dec 2019 20:17:05 +0200
Laurent Pinchart <[e-mail]> wrote:

> Hi Boris,
> 
> Thank you for the patch.
> 
> On Tue, Dec 03, 2019 at 03:15:12PM +0100, 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 <[e-mail]>
> > Reviewed-by: Neil Armstrong <[e-mail]>
> > ---
> > Changes in v4:
> > * Fix the doc
> > * Kill default helpers (inlined)  
> 
> I liked the default helpers, inlining their content makes the code more
> difficult to follow in my opinion.

I'll go back to this approach then. Should I keep the original helper
names even though they're not globally visible (and should probably
never be)?

Laurent Pinchart Dec. 4, 2019, 9:12 a.m. UTC | #3

Hi Boris,

On Wed, Dec 04, 2019 at 10:03:02AM +0100, Boris Brezillon wrote:
> On Tue, 3 Dec 2019 20:17:05 +0200 Laurent Pinchart wrote:
> > On Tue, Dec 03, 2019 at 03:15:12PM +0100, 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 <[e-mail]>
> > > Reviewed-by: Neil Armstrong <[e-mail]>
> > > ---
> > > Changes in v4:
> > > * Fix the doc
> > > * Kill default helpers (inlined)  
> > 
> > I liked the default helpers, inlining their content makes the code more
> > difficult to follow in my opinion.
> 
> I'll go back to this approach then. Should I keep the original helper
> names even though they're not globally visible (and should probably
> never be)?

I agree they should probably never be visible, and I trust your
judgement on naming. Please double-check the documentation though, to
ensure that it matches the implementation.

Boris Brezillon Dec. 4, 2019, 9:42 a.m. UTC | #4

On Wed, 4 Dec 2019 11:12:55 +0200
Laurent Pinchart <[e-mail]> wrote:

> Hi Boris,
> 
> On Wed, Dec 04, 2019 at 10:03:02AM +0100, Boris Brezillon wrote:
> > On Tue, 3 Dec 2019 20:17:05 +0200 Laurent Pinchart wrote:  
> > > On Tue, Dec 03, 2019 at 03:15:12PM +0100, 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 <[e-mail]>
> > > > Reviewed-by: Neil Armstrong <[e-mail]>
> > > > ---
> > > > Changes in v4:
> > > > * Fix the doc
> > > > * Kill default helpers (inlined)    
> > > 
> > > I liked the default helpers, inlining their content makes the code more
> > > difficult to follow in my opinion.  
> > 
> > I'll go back to this approach then. Should I keep the original helper
> > names even though they're not globally visible (and should probably
> > never be)?  
> 
> I agree they should probably never be visible, and I trust your
> judgement on naming. Please double-check the documentation though, to
> ensure that it matches the implementation.
> 

Is there any point keeping the documentation if they're not exposed?

Laurent Pinchart Dec. 4, 2019, 10:38 a.m. UTC | #5

Hi Boris,

On Wed, Dec 04, 2019 at 10:42:07AM +0100, Boris Brezillon wrote:
> On Wed, 4 Dec 2019 11:12:55 +0200 Laurent Pinchart wrote:
> > On Wed, Dec 04, 2019 at 10:03:02AM +0100, Boris Brezillon wrote:
> > > On Tue, 3 Dec 2019 20:17:05 +0200 Laurent Pinchart wrote:  
> > > > On Tue, Dec 03, 2019 at 03:15:12PM +0100, 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 <[e-mail]>
> > > > > Reviewed-by: Neil Armstrong <[e-mail]>
> > > > > ---
> > > > > Changes in v4:
> > > > > * Fix the doc
> > > > > * Kill default helpers (inlined)    
> > > > 
> > > > I liked the default helpers, inlining their content makes the code more
> > > > difficult to follow in my opinion.  
> > > 
> > > I'll go back to this approach then. Should I keep the original helper
> > > names even though they're not globally visible (and should probably
> > > never be)?  
> > 
> > I agree they should probably never be visible, and I trust your
> > judgement on naming. Please double-check the documentation though, to
> > ensure that it matches the implementation.
> 
> Is there any point keeping the documentation if they're not exposed?

I'll let you decide on that, depending on if the documentation could
bring value or if the functions would be so trivial that it would be
overkill.

Patch

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 14aeaf736321..02f8034f5240 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>
@@ -1015,6 +1016,44 @@  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 29c3115bf9e2..e2f7f336a2d2 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 b6517b4fa3d1..bf5a2243a115 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 +90,48 @@  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);
+
+		return state ? &state->base : NULL;
+	}
+
+	if (WARN_ON(!bridge->base.state))
+		return NULL;
+
+	state = kzalloc(sizeof(*state), GFP_KERNEL);
+	if (!state)
+		return NULL;
+
+	__drm_atomic_helper_bridge_duplicate_state(bridge, state);
+
+	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
+		kfree(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 +157,7 @@  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;
 	int ret;
 
 	if (!encoder || !bridge)
@@ -135,15 +179,40 @@  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) {
+		state = bridge->funcs->atomic_reset(bridge);
+	} else {
+		state = kzalloc(sizeof(*state), GFP_KERNEL);
+		if (state)
+			__drm_atomic_helper_bridge_reset(bridge, state);
+		else
+			state = ERR_PTR(-ENOMEM);
+	}
+
+	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 +224,8 @@  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);
 
@@ -516,6 +587,41 @@  void drm_atomic_bridge_chain_enable(struct drm_bridge *bridge,
 }
 EXPORT_SYMBOL(drm_atomic_bridge_chain_enable);
 
+/**
+ * __drm_atomic_helper_bridge_reset() - Initialize a bridge state to its
+ *					default
+ * @bridge: the bridge this state is refers to
+ * @state: bridge state to initialize
+ *
+ * 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_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);
+
 #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 b6c73fd9f55a..e08582773d6c 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 d7d714023050..db5fc18d49bd 100644
--- a/include/drm/drm_bridge.h
+++ b/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>
@@ -33,6 +35,23 @@  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 +357,49 @@  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 optional. When not implemented the core
+	 * allocates a new state and calls &__drm_atomic_helper_bridge_reset().
+	 *
+	 * 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 +442,8 @@  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 +468,12 @@  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);
@@ -491,6 +561,52 @@  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_duplicate_state(struct drm_bridge *bridge,
+						struct drm_bridge_state *new);
+
+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 (IS_ERR(obj_state))
+		return ERR_CAST(obj_state);
+
+	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,