ASoC: dmaengine: Support custom channel names

Some devices have more than just simple TX and RX DMA channels, for example
modern Samsung I2S IPs support a secondary transmit DMA stream which is
mixed into the primary stream during playback. Allow such devices to
specify the names of the channels to be requested in their dma_data.

Signed-off-by: Mark Brown <broonie@linaro.org>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>

sound/soc/soc-generic-dmaengine-pcm.c

@@ -183,6 +183,8 @@ static int dmaengine_pcm_new(struct snd_soc_pcm_runtime *rtd)
 {
 	struct dmaengine_pcm *pcm = soc_platform_to_pcm(rtd->platform);
 	const struct snd_dmaengine_pcm_config *config = pcm->config;
+	struct device *dev = rtd->platform->dev;
+	struct snd_dmaengine_dai_dma_data *dma_data;
 	struct snd_pcm_substream *substream;
 	size_t prealloc_buffer_size;
 	size_t max_buffer_size;
@@ -203,6 +205,13 @@ static int dmaengine_pcm_new(struct snd_soc_pcm_runtime *rtd)
 		if (!substream)
 			continue;
 
+		dma_data = snd_soc_dai_get_dma_data(rtd->cpu_dai, substream);
+
+		if (!pcm->chan[i] &&
+		    (pcm->flags & SND_DMAENGINE_PCM_FLAG_CUSTOM_CHANNEL_NAME))
+			pcm->chan[i] = dma_request_slave_channel(dev,
+				dma_data->chan_name);
+
 		if (!pcm->chan[i] && (pcm->flags & SND_DMAENGINE_PCM_FLAG_COMPAT)) {
 			pcm->chan[i] = dmaengine_pcm_compat_request_channel(rtd,
 				substream);
@@ -275,7 +284,9 @@ static void dmaengine_pcm_request_chan_of(struct dmaengine_pcm *pcm,
 {
 	unsigned int i;
 
-	if ((pcm->flags & SND_DMAENGINE_PCM_FLAG_NO_DT) || !dev->of_node)
+	if ((pcm->flags & (SND_DMAENGINE_PCM_FLAG_NO_DT |
+			   SND_DMAENGINE_PCM_FLAG_CUSTOM_CHANNEL_NAME)) ||
+	    !dev->of_node)
 		return;
 
 	if (pcm->flags & SND_DMAENGINE_PCM_FLAG_HALF_DUPLEX) {