[alsa-devel] [PATCH v2] ALSA: core: Allow drivers to set R/W wait time.

[Takashi Iwai]

On Mon, 02 Jul 2018 18:04:54 +0200,
Liam Girdwood wrote:
> 
> Currently ALSA core blocks userspace for about 10 seconds for PCM R/W IO.
> This needs to be configurable for modern hardware like DSPs where no
> pointer update in milliseconds can indicate terminal DSP errors.
> 
> Add a substream variable to set the wait time in ms. This allows userspace
> and drivers to recover more quickly from terminal DSP errors.
> 
> Signed-off-by: Liam Girdwood <liam.r.girdwood at linux.intel.com>
> ---
> 
> Changes since V1 :-
> 
>  o Remove API method and alow drivers to set directly.
>  o Validate time is driver supplied times.
> 
>  include/sound/pcm.h  |  1 +
>  sound/core/pcm_lib.c | 10 ++++++++--
>  2 files changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/include/sound/pcm.h b/include/sound/pcm.h
> index e054c583d3b3..edad4a506b93 100644
> --- a/include/sound/pcm.h
> +++ b/include/sound/pcm.h
> @@ -462,6 +462,7 @@ struct snd_pcm_substream {
>          /* -- timer section -- */
>  	struct snd_timer *timer;		/* timer */
>  	unsigned timer_running: 1;	/* time is running */
> +	unsigned wait_time;	/* time in ms for R/W to wait for avail */
>  	/* -- next substream -- */
>  	struct snd_pcm_substream *next;
>  	/* -- linked substreams -- */
> diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
> index 44b5ae833082..6909b896a6a1 100644
> --- a/sound/core/pcm_lib.c
> +++ b/sound/core/pcm_lib.c
> @@ -1832,12 +1832,18 @@ static int wait_for_avail(struct snd_pcm_substream *substream,
>  	if (runtime->no_period_wakeup)
>  		wait_time = MAX_SCHEDULE_TIMEOUT;
>  	else {
> -		wait_time = 10;
> +		/* use wait time from substream if available */
> +		if (substream->wait_time) {
> +			wait_time = substream->wait_time;
> +		} else {
> +			wait_time = 10 * 1000; /* 10 secs */
> +		}
> +

This seems to be msec, but...


>  		if (runtime->rate) {
>  			long t = runtime->period_size * 2 / runtime->rate;
>  			wait_time = max(t, wait_time);

... here handled as a second.

>  		}
> -		wait_time = msecs_to_jiffies(wait_time * 1000);
> +		wait_time = msecs_to_jiffies(wait_time);

... so this looks inconsistent.

Also, watch out the complaints from checkpatch.pl.


thanks,

Takashi