On Tue, 21 Jan 2020 02:54:26 +0100,
Kuninori Morimoto wrote:
>
>
> Hi ALSA ML
>
> soc-pcm has snd_pcm_limit_hw_rates() which determine rate_min/rate_max fields.
> It updates runtime->hw.rate_min/max (A) based on hw->rates (B).
>
> int snd_pcm_limit_hw_rates(struct snd_pcm_runtime *runtime)
> {
> int i;
> for (i = 0; i < (int)snd_pcm_known_rates.count; i++) {
> (B) if (runtime->hw.rates & (1 << i)) {
> (A) runtime->hw.rate_min = snd_pcm_known_rates.list[i];
> break;
> }
> }
> for (i = (int)snd_pcm_known_rates.count - 1; i >= 0; i--) {
> (B) if (runtime->hw.rates & (1 << i)) {
> (A) runtime->hw.rate_max = snd_pcm_known_rates.list[i];
> break;
> }
> }
> return 0;
> }
>
> I guess the calling timing is
>
> 1) set hw->rates
> 2) call snd_pcm_limit_hw_rates()
> 3) update hw->rate_min/max
>
> soc_pcm_init_runtime_hw() is calling it as this order
>
> static void soc_pcm_init_runtime_hw(xxx)
> {
> ...
> 1) hw->rates = snd_pcm_rate_mask_intersect(rates, cpu_stream->rates);
>
> 2) snd_pcm_limit_hw_rates(runtime);
>
> 3) hw->rate_min = max(hw->rate_min, cpu_stream->rate_min);
> hw->rate_min = max(hw->rate_min, rate_min);
> hw->rate_max = min_not_zero(hw->rate_max, cpu_stream->rate_max);
> hw->rate_max = min_not_zero(hw->rate_max, rate_max);
> }
>
> But, dpcm_fe_dai_startup() are different.
>
> static int dpcm_fe_dai_startup(xxx)
> {
> ...
> /*
> * dpcm_set_fe_runtime() updates runtime->hw.xxx
> */
> 1) 3) dpcm_set_fe_runtime(fe_substream);
> 2) snd_pcm_limit_hw_rates(runtime);
> ...
> }
>
> I guess we need fixup dpcm_fe_dai_startup() ?
A good catch.
Actually the question is whether we need snd_pcm_limit_hw_rates() call
or not. The current code in soc_pcm_init_runtime_hw() assumes that
each cpu and codec dais already set the proper rate_min and rate_max,
and narrow the range accordingly. So basically the call there is
superfluous. OTOH, in dpcm_fe_dai_startup(), the call overrides the
existing rate_min/max setup as you mentioned, so it may be wrong.
Or, better to ask -- is there any case that snd_pcm_limit_hw_rates()
is mandatory in ASoC? The snd_pcm_limit_hw_rates() is for setting up
rates_min and rates_max from rates bits. It's a function to be called
only when we know that rates bits contain the full information and
rates_min and rates_max are bogus. That is, its overriding behavior
is designed.
OTOH, if the driver sets up already valid rates_min and rates_max
values, there is no need to call this function at all.
thanks,
Takashi
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