[alsa-devel] [PATCH v4] ALSA: core: Allow drivers to set R/W wait time.

[Hui Wang]

On 2018/7/6 下午8:50, 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. 
>
> v3:-
>   o Remove driver supplied time validation.
>
>  include/sound/pcm.h  |  1 +
>  sound/core/pcm_lib.c | 17 ++++++++++++-----
>  2 files changed, 13 insertions(+), 5 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..eecbfdc7a2c9 100644
> --- a/sound/core/pcm_lib.c
> +++ b/sound/core/pcm_lib.c
> @@ -1832,12 +1832,19 @@ static int wait_for_avail(struct snd_pcm_substream *substream,
>  	if (runtime->no_period_wakeup)
>  		wait_time = MAX_SCHEDULE_TIMEOUT;
>  	else {
> -		wait_time = 10;
> -		if (runtime->rate) {
> -			long t = runtime->period_size * 2 / runtime->rate;
> -			wait_time = max(t, wait_time);
> +		/* use wait time from substream if available */
> +		if (substream->wait_time) {
> +			wait_time = substream->wait_time;

I investigated the sof driver recently,  and found this  patch is a
little bit confused,  if substream->wait_time is set, why don't  convert
the wait_time to jiffies here? Is it a bug or an on-purpose design?

Thanks,

Hui.


> +		} else {
> +			wait_time = 10;
> +
> +			if (runtime->rate) {
> +				long t = runtime->period_size * 2 /
> +					 runtime->rate;
> +				wait_time = max(t, wait_time);
> +			}
> +			wait_time = msecs_to_jiffies(wait_time * 1000);
>  		}
> -		wait_time = msecs_to_jiffies(wait_time * 1000);
>  	}
>  
>  	for (;;) {