Re: [alsa-devel] [PATCH 1/1] ASoC: soc-pcm: DPCM cares BE channel constraint

[Jerome Brunet]

On Wed, 2018-06-20 at 18:25 +0900, jiada_wang@xxxxxxxxxx wrote:
> From: Jiada Wang <jiada_wang@xxxxxxxxxx>
> 
> Current DPCM is caring only FE channel configuration. Sometimes
> it will be trouble if user selects channel which isn't supported
> by BE.
> 
> This patch adds new .dpcm_merged_chan on struct snd_soc_dai_link.
> DPCM will use FE / BE merged channel if struct snd_soc_dai_link
> has it.
> 
> Signed-off-by: Jiada Wang <jiada_wang@xxxxxxxxxx>
> ---
>  include/sound/soc.h |  2 ++
>  sound/soc/soc-pcm.c | 46 +++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 48 insertions(+)
> 
> diff --git a/include/sound/soc.h b/include/sound/soc.h
> index 1378dcd2128a..f7579f82cc00 100644
> --- a/include/sound/soc.h
> +++ b/include/sound/soc.h
> @@ -957,6 +957,8 @@ struct snd_soc_dai_link {
>  
>  	/* DPCM used FE & BE merged format */
>  	unsigned int dpcm_merged_format:1;
> +	/* DPCM used FE & BE merged channel */
> +	unsigned int dpcm_merged_chan:1;

Jiada, Mark,

Do you think we could extend this flag to let the link choose whether the merge
should be performed on the codec dais (as done here) or on the backend cpu dais
?

I have more less the same need as Jiada but since my card uses multicodec links,
merging on the codec dais does not work for me.

Like in soc_pcm_init_runtime_hw(), we can't enforce channels min/max based on
the codec when there is multiple codecs on the link.

Thx
Regards

Jerome

>  
>  	/* pmdown_time is ignored at stop */
>  	unsigned int ignore_pmdown_time:1;
> diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
> index 45b52f7b9690..19ebfc958b9d 100644
> --- a/sound/soc/soc-pcm.c
> +++ b/sound/soc/soc-pcm.c
> @@ -1715,6 +1715,46 @@ static u64 dpcm_runtime_base_format(struct snd_pcm_substream *substream)
>  	return formats;
>  }
>  
> +static void dpcm_runtime_base_chan(struct snd_pcm_substream *substream,
> +				   unsigned int *channels_min,
> +				   unsigned int *channels_max)
> +{
> +	struct snd_soc_pcm_runtime *fe = substream->private_data;
> +	struct snd_soc_dpcm *dpcm;
> +	int stream = substream->stream;
> +
> +	if (!fe->dai_link->dpcm_merged_chan)
> +		return;
> +
> +	*channels_min = 0;
> +	*channels_max = UINT_MAX;
> +
> +	/*
> +	 * It returns merged BE codec channel;
> +	 * if FE want to use it (= dpcm_merged_chan)
> +	 */
> +
> +	list_for_each_entry(dpcm, &fe->dpcm[stream].be_clients, list_be) {
> +		struct snd_soc_pcm_runtime *be = dpcm->be;
> +		struct snd_soc_dai_driver *codec_dai_drv;
> +		struct snd_soc_pcm_stream *codec_stream;
> +		int i;
> +
> +		for (i = 0; i < be->num_codecs; i++) {
> +			codec_dai_drv = be->codec_dais[i]->driver;
> +			if (stream == SNDRV_PCM_STREAM_PLAYBACK)
> +				codec_stream = &codec_dai_drv->playback;
> +			else
> +				codec_stream = &codec_dai_drv->capture;
> +
> +			*channels_min = max(*channels_min,
> +					    codec_stream->channels_min);
> +			*channels_max = min(*channels_max,
> +					    codec_stream->channels_max);
> +		}
> +	}
> +}
> +
>  static void dpcm_set_fe_runtime(struct snd_pcm_substream *substream)
>  {
>  	struct snd_pcm_runtime *runtime = substream->runtime;
> @@ -1722,11 +1762,17 @@ static void dpcm_set_fe_runtime(struct snd_pcm_substream *substream)
>  	struct snd_soc_dai *cpu_dai = rtd->cpu_dai;
>  	struct snd_soc_dai_driver *cpu_dai_drv = cpu_dai->driver;
>  	u64 format = dpcm_runtime_base_format(substream);
> +	unsigned int channels_min = 0, channels_max = UINT_MAX;
>  
>  	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
>  		dpcm_init_runtime_hw(runtime, &cpu_dai_drv->playback, format);
>  	else
>  		dpcm_init_runtime_hw(runtime, &cpu_dai_drv->capture, format);
> +
> +	dpcm_runtime_base_chan(substream, &channels_min, &channels_max);
> +
> +	runtime->hw.channels_min = max(channels_min, runtime->hw.channels_min);
> +	runtime->hw.channels_max = min(channels_max, runtime->hw.channels_max);
>  }
>  
>  static int dpcm_fe_dai_do_trigger(struct snd_pcm_substream *substream, int cmd);