On Wed, 14 Mar 2018 21:44:40 +0100,
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@xxxxxxxxxxxxxxx>
The idea looks good, though, a bit of nitpicking:
> ---
> include/sound/pcm.h | 6 ++++++
> sound/core/pcm_lib.c | 15 ++++++++++-----
> 2 files changed, 16 insertions(+), 5 deletions(-)
>
> diff --git a/include/sound/pcm.h b/include/sound/pcm.h
> index e054c583d3b3..e4694684c524 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 */
I'd name wait_timeout, which is slightly clearer.
> /* -- next substream -- */
> struct snd_pcm_substream *next;
> /* -- linked substreams -- */
> @@ -579,6 +580,11 @@ int snd_pcm_start(struct snd_pcm_substream *substream);
> int snd_pcm_stop(struct snd_pcm_substream *substream, snd_pcm_state_t status);
> int snd_pcm_drain_done(struct snd_pcm_substream *substream);
> int snd_pcm_stop_xrun(struct snd_pcm_substream *substream);
> +static inline void snd_pcm_wait_time(struct snd_pcm_substream *substream,
> + unsigned wait_time)
> +{
> + substream->wait_time = wait_time;
> +}
IMO, it's a simple one parameter, and no need wrapping with an inline
function.
> #ifdef CONFIG_PM
> int snd_pcm_suspend(struct snd_pcm_substream *substream);
> int snd_pcm_suspend_all(struct snd_pcm *pcm);
> diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
> index a83152e7d387..2ee76c70f55f 100644
> --- a/sound/core/pcm_lib.c
> +++ b/sound/core/pcm_lib.c
> @@ -1839,12 +1839,17 @@ 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 = msecs_to_jiffies(substream->wait_time);
> + } 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);
This can go bad when wait_time is shorter than the period time.
Some validation is needed?
Also, how is user-space supposed to set the new parameter?
thanks,
Takashi
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