[alsa-devel] ASoC: multicodec: No matching channels with system with DACs and ADCs on same bus

[Liam Girdwood]

On Tue, 2015-11-10 at 09:12 -0800, Caleb Crome wrote:
> Hi again,
>   I have a system that has separate DACs and ADCs, as opposed to
> bidirectional CODECS.
> 
> The ADCs have a snd_soc_dai_driver structure that have a .capture
> field defined with a .rates parameter, and the DACs have a
> snd_soc_dai_driver structure that have a .playback field defined with
> a .rates parameter.
> 
> However, the ADCs have no .playback.rates, and the DACs have no
> .capture.rates. Even though the ADC can record at a given rate and the
> DAC can play at that same rate, the soc_pcm_init_runtime_hw function
> calculates the rates in this loop:
> 
> ------------------------------
>     /* first calculate min/max only for CODECs in the DAI link */
>     for (i = 0; i < rtd->num_codecs; i++) {
>         codec_dai_drv = rtd->codec_dais[i]->driver;
>         if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
>             codec_stream = &codec_dai_drv->playback;
>         else
>             codec_stream = &codec_dai_drv->capture;
>         chan_min = max(chan_min, codec_stream->channels_min);
>         chan_max = min(chan_max, codec_stream->channels_max);
>         rate_min = max(rate_min, codec_stream->rate_min);
>         rate_max = min_not_zero(rate_max, codec_stream->rate_max);
>         formats &= codec_stream->formats;
>         rates = snd_pcm_rate_mask_intersect(codec_stream->rates, rates);
>     }
> ------------------------------
> 
> which can't work out that one side is play only and the other is
> record only, yet they do in fact have matching rates.  So, I get a "no
> matching channels" error.
> 
> 
> Here are my example drivers declarations:
> for the ADC:
> ----------------------
> static struct snd_soc_dai_driver cs53l30_dai = {
>     .name = "cs53l30-hifi",
>     .capture = {
>         .stream_name = "Capture",
>         .channels_min = 4,
>         .channels_max = 16,
>         .rates = SNDRV_PCM_RATE_16000,
>         .formats =SNDRV_PCM_FMTBIT_S16_LE,
>     },
> };
> --------------------
> 
> and for the DAC
> 
> ----------------------
> static struct snd_soc_dai_driver tlv320dac3100_dai = {
>     .name = "tlv320dac3100-hifi",
>     .playback = {
>         .stream_name = "Playback",
>         .channels_min = 2,
>         .channels_max = 16,
>         .rates = SNDRV_PCM_RATE_16000,
>         .formats =SNDRV_PCM_FMTBIT_S16_LE,
>     },
>     .ops = &tlv320dac3100_dai_ops,
> };
> ------------------------------
> 
> I was able to fake it out by adding a .playback field to my ADC with 0
> channels, and a .capture field to my DAC with 0 channels.
> 
> My question is: what's the right way to manage this?  I assume we
> should probably tweak soc_pcm_init_runtime_hw, right?

Not sure why this is not working for you. There are other DAI drivers
upstream that are unidirectional and work fine. 

Are you combining both unidirectional DAIs above into a single
bidirectional DAI ?

Liam