Re: [PATCH v3 07/21] drm/bridge: Make the bridge chain a double-linked list

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Hi,


On 25/10/2019 15:29, Neil Armstrong wrote:
> On 23/10/2019 17:44, Boris Brezillon wrote:
>> So that each element in the chain can easily access its predecessor.
>> This will be needed to support bus format negotiation between elements
>> of the bridge chain.
>>
>> Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
>> ---
>> Changes in v3:
>> * None
>>
>> Changes in v2:
>> * Adjust things to the "dummy encoder bridge" change (patch 2 in this
>>   series)
>> ---
>>  drivers/gpu/drm/drm_bridge.c  | 171 ++++++++++++++++++++++------------
>>  drivers/gpu/drm/drm_encoder.c |  16 +---
>>  include/drm/drm_bridge.h      |  12 ++-
>>  include/drm/drm_encoder.h     |   9 +-
>>  4 files changed, 135 insertions(+), 73 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
>> index 54c874493c57..c5cf8a9c4237 100644
>> --- a/drivers/gpu/drm/drm_bridge.c
>> +++ b/drivers/gpu/drm/drm_bridge.c

[...]

>>  
>> @@ -426,15 +471,23 @@ EXPORT_SYMBOL(drm_atomic_bridge_chain_post_disable);
>>  void drm_atomic_bridge_chain_pre_enable(struct drm_bridge *bridge,
>>  					struct drm_atomic_state *state)
>>  {
>> +	struct drm_encoder *encoder;
>> +	struct drm_bridge *iter;
>> +
>>  	if (!bridge)
>>  		return;
>>  
>> -	drm_atomic_bridge_chain_pre_enable(bridge->next, state);
>> +	encoder = bridge->encoder;
>> +	list_for_each_entry_reverse(iter, &bridge->encoder->bridge_chain,
>> +				    chain_node) {

This should use the encoder local variable in list_for_each_entry_reverse()

>> +		if (iter->funcs->atomic_pre_enable)
>> +			iter->funcs->atomic_pre_enable(iter, state);
>> +		else if (iter->funcs->pre_enable)
>> +			iter->funcs->pre_enable(iter);
>>  
>> -	if (bridge->funcs->atomic_pre_enable)
>> -		bridge->funcs->atomic_pre_enable(bridge, state);
>> -	else if (bridge->funcs->pre_enable)
>> -		bridge->funcs->pre_enable(bridge);
>> +		if (iter == bridge)
>> +			break;
>> +	}
>>  }
>>  EXPORT_SYMBOL(drm_atomic_bridge_chain_pre_enable);
>>  
>> @@ -453,15 +506,19 @@ EXPORT_SYMBOL(drm_atomic_bridge_chain_pre_enable);
>>  void drm_atomic_bridge_chain_enable(struct drm_bridge *bridge,
>>  				    struct drm_atomic_state *state)
>>  {
>> +	struct drm_encoder *encoder;
>> +
>>  	if (!bridge)
>>  		return;
>>  
>> -	if (bridge->funcs->atomic_enable)
>> -		bridge->funcs->atomic_enable(bridge, state);
>> -	else if (bridge->funcs->enable)
>> -		bridge->funcs->enable(bridge);
>> -
>> -	drm_atomic_bridge_chain_enable(bridge->next, state);
>> +	encoder = bridge->encoder;
>> +	list_for_each_entry_from(bridge, &bridge->encoder->bridge_chain,
>> +				 chain_node) {

This should use encoder instead of bridge->encoder otherwise bridge will
change and bridge->encoder->bridge_chain won't be valid during the for_each and
cause the following :

[   79.082861] WARNING: CPU: 2 PID: 1999 at drivers/gpu/drm/drm_bridge.c:607 drm_atomic_bridge_chain_enable+0xac/0xc0
...
[   79.210153]  drm_atomic_bridge_chain_enable+0xac/0xc0
[   79.215156]  drm_atomic_helper_commit_modeset_enables+0x138/0x248
[   79.221190]  drm_atomic_helper_commit_tail_rpm+0x2c/0x78
[   79.226452]  commit_tail+0x50/0xc0
[   79.229815]  drm_atomic_helper_commit+0xe8/0x168
[   79.234386]  drm_atomic_commit+0x48/0x58
[   79.238269]  drm_client_modeset_commit_atomic.isra.15+0x184/0x220
[   79.244305]  drm_client_modeset_commit_force+0x64/0x1a0
[   79.249482]  drm_fb_helper_restore_fbdev_mode_unlocked+0x70/0xe8
[   79.255432]  drm_fbdev_client_restore+0x14/0x20
[   79.259920]  drm_client_dev_restore+0x80/0xd8
[   79.264231]  drm_lastclose+0x4c/0x58
[   79.267765]  drm_release+0xa8/0x178

>> +		if (bridge->funcs->atomic_enable)
>> +			bridge->funcs->atomic_enable(bridge, state);
>> +		else if (bridge->funcs->enable)
>> +			bridge->funcs->enable(bridge);
>> +	}
>>  }
>>  EXPORT_SYMBOL(drm_atomic_bridge_chain_enable);
>>  
>> diff --git a/drivers/gpu/drm/drm_encoder.c b/drivers/gpu/drm/drm_encoder.c
>> index 4fe9e723e227..e555281f43d4 100644
>> --- a/drivers/gpu/drm/drm_encoder.c
>> +++ b/drivers/gpu/drm/drm_encoder.c
>> @@ -140,6 +140,7 @@ int drm_encoder_init(struct drm_device *dev,
>>  		goto out_put;
>>  	}
>>  
>> +	INIT_LIST_HEAD(&encoder->bridge_chain);
>>  	list_add_tail(&encoder->head, &dev->mode_config.encoder_list);
>>  	encoder->index = dev->mode_config.num_encoder++;
>>  
>> @@ -160,23 +161,16 @@ EXPORT_SYMBOL(drm_encoder_init);
>>  void drm_encoder_cleanup(struct drm_encoder *encoder)
>>  {
>>  	struct drm_device *dev = encoder->dev;
>> +	struct drm_bridge *bridge, *next;
>>  
>>  	/* Note that the encoder_list is considered to be static; should we
>>  	 * remove the drm_encoder at runtime we would have to decrement all
>>  	 * the indices on the drm_encoder after us in the encoder_list.
>>  	 */
>>  
>> -	if (encoder->bridge) {
>> -		struct drm_bridge *bridge;
>> -		struct drm_bridge *next;
>> -
>> -		bridge = drm_bridge_chain_get_first_bridge(encoder);
>> -		while (bridge) {
>> -			next = bridge->next;
>> -			drm_bridge_detach(bridge);
>> -			bridge = next;
>> -		}
>> -	}
>> +	list_for_each_entry_safe(bridge, next, &encoder->bridge_chain,
>> +				 chain_node)
>> +		drm_bridge_detach(bridge);
>>  
>>  	drm_mode_object_unregister(dev, &encoder->base);
>>  	kfree(encoder->name);
>> diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
>> index 27eef63ce0ff..3ab16c95e59e 100644
>> --- a/include/drm/drm_bridge.h
>> +++ b/include/drm/drm_bridge.h
>> @@ -384,8 +384,8 @@ struct drm_bridge {
>>  	struct drm_device *dev;
>>  	/** @encoder: encoder to which this bridge is connected */
>>  	struct drm_encoder *encoder;
>> -	/** @next: the next bridge in the encoder chain */
>> -	struct drm_bridge *next;
>> +	/** @chain_node: used to form a bridge chain */
>> +	struct list_head chain_node;
>>  #ifdef CONFIG_OF
>>  	/** @of_node: device node pointer to the bridge */
>>  	struct device_node *of_node;
>> @@ -420,7 +420,10 @@ int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
>>  static inline struct drm_bridge *
>>  drm_bridge_chain_get_next_bridge(struct drm_bridge *bridge)
>>  {
>> -	return bridge->next;
>> +	if (list_is_last(&bridge->chain_node, &bridge->encoder->bridge_chain))
>> +		return NULL;
>> +
>> +	return list_next_entry(bridge, chain_node);
>>  }
>>  
>>  /**
>> @@ -434,7 +437,8 @@ drm_bridge_chain_get_next_bridge(struct drm_bridge *bridge)
>>  static inline struct drm_bridge *
>>  drm_bridge_chain_get_first_bridge(struct drm_encoder *encoder)
>>  {
>> -	return encoder->bridge;
>> +	return list_first_entry_or_null(&encoder->bridge_chain,
>> +					struct drm_bridge, chain_node);
>>  }
>>  
>>  bool drm_bridge_chain_mode_fixup(struct drm_bridge *bridge,
>> diff --git a/include/drm/drm_encoder.h b/include/drm/drm_encoder.h
>> index f06164f44efe..9b3dde177c81 100644
>> --- a/include/drm/drm_encoder.h
>> +++ b/include/drm/drm_encoder.h
>> @@ -172,7 +172,14 @@ struct drm_encoder {
>>  	 * &drm_connector_state.crtc.
>>  	 */
>>  	struct drm_crtc *crtc;
>> -	struct drm_bridge *bridge;
>> +
>> +	/**
>> +	 * @bridge_chain: Bridges attached to this encoder. The first entry of
>> +	 * this list is always &drm_encoder.bridge. It may be followed by other
>> +	 * bridge entities.
>> +	 */
>> +	struct list_head bridge_chain;
>> +
>>  	const struct drm_encoder_funcs *funcs;
>>  	const struct drm_encoder_helper_funcs *helper_private;
>>  };
>>
> 
> Reviewed-by: Neil Armstrong <narmstrong@xxxxxxxxxxxx>
> 

With these fixed, you can keep my Reviewed-by

Neil



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