[alsa-devel] [PATCH 49/49] firewire/bebob: Add a workaround for M-Audio special Firewire series

[Takashi Iwai]

At Fri, 25 Apr 2014 22:45:30 +0900,
Takashi Sakamoto wrote:
> 
> In post commit, a quirk of this firmware about transactions is reported.
> This commit apply a workaround for this quirk.
> 
> They often fail transactions due to gap_count mismatch. This state is changed
> by generating bus reset.
> 
> The fw_schedule_bus_reset() is an exported symbol in firewire-core. But there
> are no header for public. This commit moves its prototype from
> drivers/firewire/core.h to include/linux/firewire.h.
> 
> This mismatch still affects bus management before generating this bus reset.
> It still takes a time to call driver's probe() because transactions are still
> often failed.
> 
> Signed-off-by: Takashi Sakamoto <o-takashi at sakamocchi.jp>

Hrm, I should have taken a deeper review.  This change was slipped to
my tree without Stefan's ack.
Stefan, is it OK to keep this change as is?


thanks,

Takashi

> ---
>  drivers/firewire/core.h      |  1 -
>  include/linux/firewire.h     |  3 +++
>  sound/firewire/bebob/bebob.c | 32 ++++++++++++++++++++++++++++----
>  sound/firewire/bebob/bebob.h |  1 +
>  4 files changed, 32 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/firewire/core.h b/drivers/firewire/core.h
> index c98764a..870044e 100644
> --- a/drivers/firewire/core.h
> +++ b/drivers/firewire/core.h
> @@ -118,7 +118,6 @@ int fw_card_add(struct fw_card *card,
>  		u32 max_receive, u32 link_speed, u64 guid);
>  void fw_core_remove_card(struct fw_card *card);
>  int fw_compute_block_crc(__be32 *block);
> -void fw_schedule_bus_reset(struct fw_card *card, bool delayed, bool short_reset);
>  void fw_schedule_bm_work(struct fw_card *card, unsigned long delay);
>  
>  /* -cdev */
> diff --git a/include/linux/firewire.h b/include/linux/firewire.h
> index c3683bd..d4b7683 100644
> --- a/include/linux/firewire.h
> +++ b/include/linux/firewire.h
> @@ -367,6 +367,9 @@ static inline int fw_stream_packet_destination_id(int tag, int channel, int sy)
>  	return tag << 14 | channel << 8 | sy;
>  }
>  
> +void fw_schedule_bus_reset(struct fw_card *card, bool delayed,
> +			   bool short_reset);
> +
>  struct fw_descriptor {
>  	struct list_head link;
>  	size_t length;
> diff --git a/sound/firewire/bebob/bebob.c b/sound/firewire/bebob/bebob.c
> index e1dd421..31b96b7 100644
> --- a/sound/firewire/bebob/bebob.c
> +++ b/sound/firewire/bebob/bebob.c
> @@ -247,10 +247,26 @@ bebob_probe(struct fw_unit *unit,
>  	if (err < 0)
>  		goto error;
>  
> -	err = snd_card_register(card);
> -	if (err < 0) {
> -		snd_bebob_stream_destroy_duplex(bebob);
> -		goto error;
> +	if (!bebob->maudio_special_quirk) {
> +		err = snd_card_register(card);
> +		if (err < 0) {
> +			snd_bebob_stream_destroy_duplex(bebob);
> +			goto error;
> +		}
> +	} else {
> +		/*
> +		 * This is a workaround. This bus reset seems to have an effect
> +		 * to make devices correctly handling transactions. Without
> +		 * this, the devices have gap_count mismatch. This causes much
> +		 * failure of transaction.
> +		 *
> +		 * Just after registration, user-land application receive
> +		 * signals from dbus and starts I/Os. To avoid I/Os till the
> +		 * future bus reset, registration is done in next update().
> +		 */
> +		bebob->deferred_registration = true;
> +		fw_schedule_bus_reset(fw_parent_device(bebob->unit)->card,
> +				      false, true);
>  	}
>  
>  	dev_set_drvdata(&unit->device, bebob);
> @@ -273,6 +289,14 @@ bebob_update(struct fw_unit *unit)
>  
>  	fcp_bus_reset(bebob->unit);
>  	snd_bebob_stream_update_duplex(bebob);
> +
> +	if (bebob->deferred_registration) {
> +		if (snd_card_register(bebob->card) < 0) {
> +			snd_bebob_stream_destroy_duplex(bebob);
> +			snd_card_free(bebob->card);
> +		}
> +		bebob->deferred_registration = false;
> +	}
>  }
>  
>  static void bebob_remove(struct fw_unit *unit)
> diff --git a/sound/firewire/bebob/bebob.h b/sound/firewire/bebob/bebob.h
> index 4a54e74..91b26b0 100644
> --- a/sound/firewire/bebob/bebob.h
> +++ b/sound/firewire/bebob/bebob.h
> @@ -109,6 +109,7 @@ struct snd_bebob {
>  
>  	/* for M-Audio special devices */
>  	void *maudio_special_quirk;
> +	bool deferred_registration;
>  };
>  
>  static inline int
> -- 
> 1.8.3.2
>