ASoC: soc-pcm: DPCM cares BE channel constraint

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@mentor.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

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;
 
 	/* pmdown_time is ignored at stop */
 	unsigned int ignore_pmdown_time:1;

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);