On Mon, 10 Feb 2020 15:28:44 +0100,
Peter Ujfalusi wrote:
>
> Hi Takashi,
>
> >> --- a/sound/soc/soc-pcm.c
> >> +++ b/sound/soc/soc-pcm.c
> >> @@ -1151,7 +1151,7 @@ static snd_pcm_uframes_t soc_pcm_pointer(struct snd_pcm_substream *substream)
> >> }
> >> delay += codec_delay;
> >>
> >> - runtime->delay = delay;
> >> + runtime->delay += delay;
> >
> > Is it correct?
> > delay already takes runtime->delay as its basis, so it'll result in a
> > double.
>
> The delay here is coming from the DAI and the codec.
> The runtime->delay hold the PCM (DMA) caused delay.
Well, let's take a look at soc_pcm_pointer():
/* clearing the previous total delay */
runtime->delay = 0;
offset = snd_soc_pcm_component_pointer(substream);
/* base delay if assigned in pointer callback */
delay = runtime->delay;
delay += snd_soc_dai_delay(cpu_dai, substream);
for_each_rtd_codec_dai(rtd, i, codec_dai) {
codec_delay = max(codec_delay,
snd_soc_dai_delay(codec_dai, substream));
}
delay += codec_delay;
runtime->delay = delay;
So, the code reads the current runtime->delay and saves it as delay
variable. Then it adds the max delay from codec DAIs, and stores back
to runtime->delay.
If we change the last line to
runtime->delay += delay;
it'll add to the already existing value again, so it'll be doubly if
runtime->delay was non-zero beforehand.
That said, judging from the code, I believe the current soc-pcm.c code
needs no change.
thanks,
Takashi
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