[alsa-devel] [PATCH 7/8] ALSA: pcm: Add card sync_irq field

[Pierre-Louis Bossart]

On 11/17/19 2:53 AM, Takashi Iwai wrote:
> Many PCI and other drivers performs snd_pcm_period_elapsed() simply in
> its interrupt handler, so the sync_stop operation is just to call
> synchronize_irq().  Instead of putting this call multiple times,
> introduce the common card->sync_irq field.  When this field is set,
> PCM core performs synchronize_irq() for sync-stop operation.  Each
> driver just needs to copy its local IRQ number to card->sync_irq, and
> that's all we need.

Maybe a red-herring or complete non-sense, but I wonder if this is going 
to get in the way of Ranjani's multi-client work, where we could have 
multiple cards created but with a single IRQ handled by the parent PCI 
device?

Ranjani, you may want to double-check this and chime in, thanks!

> 
> Signed-off-by: Takashi Iwai <tiwai at suse.de>
> ---
>   include/sound/core.h    | 1 +
>   sound/core/init.c       | 1 +
>   sound/core/pcm_native.c | 2 ++
>   3 files changed, 4 insertions(+)
> 
> diff --git a/include/sound/core.h b/include/sound/core.h
> index ee238f100f73..af3dce956c17 100644
> --- a/include/sound/core.h
> +++ b/include/sound/core.h
> @@ -117,6 +117,7 @@ struct snd_card {
>   	struct device card_dev;		/* cardX object for sysfs */
>   	const struct attribute_group *dev_groups[4]; /* assigned sysfs attr */
>   	bool registered;		/* card_dev is registered? */
> +	int sync_irq;			/* assigned irq, used for PCM sync */
>   	wait_queue_head_t remove_sleep;
>   
>   #ifdef CONFIG_PM
> diff --git a/sound/core/init.c b/sound/core/init.c
> index db99b7fad6ad..faa9f03c01ca 100644
> --- a/sound/core/init.c
> +++ b/sound/core/init.c
> @@ -215,6 +215,7 @@ int snd_card_new(struct device *parent, int idx, const char *xid,
>   	init_waitqueue_head(&card->power_sleep);
>   #endif
>   	init_waitqueue_head(&card->remove_sleep);
> +	card->sync_irq = -1;
>   
>   	device_initialize(&card->card_dev);
>   	card->card_dev.parent = parent;
> diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
> index 163d621ff238..1fe581167b7b 100644
> --- a/sound/core/pcm_native.c
> +++ b/sound/core/pcm_native.c
> @@ -574,6 +574,8 @@ static void snd_pcm_sync_stop(struct snd_pcm_substream *substream)
>   		substream->runtime->stop_operating = false;
>   		if (substream->ops->sync_stop)
>   			substream->ops->sync_stop(substream);
> +		else if (substream->pcm->card->sync_irq > 0)
> +			synchronize_irq(substream->pcm->card->sync_irq);
>   	}
>   }
>   
>