ASoC: dmaengine_pcm: Add support for packed transfers

dmaengine_pcm currently only supports setups where FIFO reads/writes
correspond to exactly one sample, eg 16-bit sample data is transferred
via 16-bit FIFO accesses, 32-bit data via 32-bit accesses.

This patch adds support for setups with fixed width FIFOs where
multiple samples are packed into a larger word.

For example setups with a 32-bit wide FIFO register that expect
16-bit sample transfers to be done with the left+right sample data
packed into a 32-bit word.

Support for packed transfers is controlled via the
SND_DMAENGINE_PCM_DAI_FLAG_PACK flag in snd_dmaengine_dai_dma_data.flags

If this flag is set dmaengine_pcm doesn't put any restriction on the
supported formats and sets the DMA transfer width to undefined.

This means control over the constraints is now transferred to the DAI
driver and it's responsible to provide proper configuration and
check for possible corner cases that aren't handled by the ALSA core.

Signed-off-by: Matthias Reichl <hias@horus.com>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Tested-by: Martin Sperl <kernel@martin.sperl.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 9 insertions, 2 deletions

diff --git a/sound/core/pcm_dmaengine.c b/sound/core/pcm_dmaengine.c
index 697c166acf05..8eb58c709b14 100644
--- a/sound/core/pcm_dmaengine.c
+++ b/sound/core/pcm_dmaengine.c
@@ -106,8 +106,9 @@ EXPORT_SYMBOL_GPL(snd_hwparams_to_dma_slave_config);
  * direction of the substream. If the substream is a playback stream the dst
  * fields will be initialized, if it is a capture stream the src fields will be
  * initialized. The {dst,src}_addr_width field will only be initialized if the
- * addr_width field of the DAI DMA data struct is not equal to
- * DMA_SLAVE_BUSWIDTH_UNDEFINED.
+ * SND_DMAENGINE_PCM_DAI_FLAG_PACK flag is set or if the addr_width field of
+ * the DAI DMA data struct is not equal to DMA_SLAVE_BUSWIDTH_UNDEFINED. If
+ * both conditions are met the latter takes priority.
  */
 void snd_dmaengine_pcm_set_config_from_dai_data(
 	const struct snd_pcm_substream *substream,
@@ -117,11 +118,17 @@ void snd_dmaengine_pcm_set_config_from_dai_data(
 	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
 		slave_config->dst_addr = dma_data->addr;
 		slave_config->dst_maxburst = dma_data->maxburst;
+		if (dma_data->flags & SND_DMAENGINE_PCM_DAI_FLAG_PACK)
+			slave_config->dst_addr_width =
+				DMA_SLAVE_BUSWIDTH_UNDEFINED;
 		if (dma_data->addr_width != DMA_SLAVE_BUSWIDTH_UNDEFINED)
 			slave_config->dst_addr_width = dma_data->addr_width;
 	} else {
 		slave_config->src_addr = dma_data->addr;
 		slave_config->src_maxburst = dma_data->maxburst;
+		if (dma_data->flags & SND_DMAENGINE_PCM_DAI_FLAG_PACK)
+			slave_config->src_addr_width =
+				DMA_SLAVE_BUSWIDTH_UNDEFINED;
 		if (dma_data->addr_width != DMA_SLAVE_BUSWIDTH_UNDEFINED)
 			slave_config->src_addr_width = dma_data->addr_width;
 	}