Hi Sakamoto-san, Mark
> > Hmm...
> > Above .be_hw_params_fixup is used to convert sampling rate or channel
> > number or some other related things between SoC / Codec as DPCM feature.
> > Thus, I can't switch to .be_hw_params_fixup to .prepare I guess.
> > But Mark, am I misunderstanding ?
>
> In 'struct snd_pcm_ops.prepare' callback, configured parameters of PCM
> substream are available via members of 'struct snd_pcm_runtime'. The
> runtime is a member of 'struct snd_pcm_substream'. It's available in
> any of .prepare callbacks in ALSA SoC part.
Thank you for detail explain.
I investigated this, and I tried to use .prepare with below system.
[44.1kHz] -> CPU -> .be_hw_params_fixup[44.1kHz -> 48kHz] -> Codec
This means, CPU converts 44.1kHz to 48kHz, and
Codec want to receive 48kHz as parameter.
On CPU/Codec both side, these got 44.1kHz from runtime.
static int cpu/codec_prepare(struct snd_pcm_substream *substream)
{
/*
* In 44.1kHz -> 48kHz convert case,
* .be_hw_params_fixup() do convert magic.
* but here .prepare, it still receive 44.1kHz
*/
printk("rate = %d\n", substream->runtime->rate);
}
On CPU side, I could get converted parameter somehow (see below),
but it has zero chance to get converted parameter on Codec side .prepare ?
Converted rate is located only struct snd_pcm_hw_params in my system (= simple-scu-card).
Current .be_hw_params_fixup() is saving converted rate/channel in struct snd_interval,
but it should save it to struct snd_soc_pcm_runtime ?
void asoc_simple_card_convert_fixup(...
struct snd_pcm_hw_params *hw_params)
{
struct snd_interval *rate = hw_param_interval(hw_params,
SNDRV_PCM_HW_PARAM_RATE);
struct snd_interval *channels = hw_param_interval(hw_params,
SNDRV_PCM_HW_PARAM_CHANNELS);
printk("------fixup\n");
if (data->convert_rate)
rate->min =
rate->max = data->convert_rate;
if (data->convert_channels)
channels->min =
channels->max = data->convert_channels;
}
---- CPU could get converted rate --------------------------
static int cpu_prepare(struct snd_pcm_substream *substream)
{
struct snd_soc_pcm_runtime *fe = substream->private_data;
/* substream->runtime->rate is still 44.1kHz here */
if (fe->dai_link->dynamic) {
int stream = substream->stream;
struct snd_soc_dpcm *dpcm;
struct snd_pcm_hw_params *be_params;
list_for_each_entry(dpcm, &fe->dpcm[stream].be_clients, list_be) {
be_params = &dpcm->hw_params;
/*
* I could receive 48kHz here as params_rate(be_params)
*/
}
}
return 0;
}
Best regards
---
Kuninori Morimoto
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