[alsa-devel] [PATCH v3] ALSA: core: Allow drivers to set R/W wait time.

[Takashi Iwai]

On Tue, 03 Jul 2018 13:22:25 +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.
> 
> V2 :-
>   o Max wait calc now in ms.
>   o checkpatch. 
> 
>  include/sound/pcm.h  |  1 +
>  sound/core/pcm_lib.c | 12 +++++++++---
>  2 files changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/include/sound/pcm.h b/include/sound/pcm.h
> index e054c583d3b3..fcdf358a25f0 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 */
> +	long 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..82a41e4d7170 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 */
> +
>  		if (runtime->rate) {
> -			long t = runtime->period_size * 2 / runtime->rate;
> +			long t = runtime->period_size * 2 /
> +				 (runtime->rate / 1000);
>  			wait_time = max(t, wait_time);
>  		}
> -		wait_time = msecs_to_jiffies(wait_time * 1000);
> +		wait_time = msecs_to_jiffies(wait_time);

I can take the patch as is, but would you like to keep runtime->rate
max check also in the case with substream->wait_time set?

Also, substream->wait_time isn't cleared at each open, right?
The driver can do it if wants, and the driver can set statically at
creation time if wants, too.


thanks,

Takashi