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ASoC: bcm2835: Add S16_LE support via packed DMA transfers

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The bcm2835-i2s driver already has support for the S16_LE format but
that format hasn't been made available because dmaengine_pcm didn't
support packed data transfers.

bcm2835-i2s needs 16-bit left+right channel data to be packed into
a 32-bit word, the FIFO register is 32-bit only and doesn't support
16-bit access.

Now that dmaengine_pcm supports packed transfers the format can
be made available by setting the SND_DMAENGINE_PCM_DAI_FLAG_PACK flag.

No further configuration is necessary:
- snd_dmaengine_dai_dma_data.addr_width is already set to
  DMA_SLAVE_BUSWIDTH_4_BYTES to force 32-bit DMA transfers
- dmaengine_pcm will pick up the S16_LE format from the DAI
  configuration and make it available since it's no longer
  masked out due to the PACK flag.
- there are no further corner cases to catch in hw_params,
  since the channel count is fixed at 2 we always have two
  16-bit stereo samples that can be transferred via 32-bit DMA

Signed-off-by: Matthias Reichl <hias@horus.com>
Tested-by: Martin Sperl <kernel@martin.sperl.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Matthias Reichl 2016-04-27 15:26:52 +02:00 committed by Mark Brown
parent cc70666c25
commit beff053c0e
1 changed files with 9 additions and 0 deletions
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9
sound/soc/bcm/bcm2835-i2s.c
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@ -690,6 +690,15 @@ static int bcm2835_i2s_probe(struct platform_device *pdev)
dev->dma_data[SNDRV_PCM_STREAM_PLAYBACK].maxburst = 2;
dev->dma_data[SNDRV_PCM_STREAM_CAPTURE].maxburst = 2;
/*
* Set the PACK flag to enable S16_LE support (2 S16_LE values
* packed into 32-bit transfers).
*/
dev->dma_data[SNDRV_PCM_STREAM_PLAYBACK].flags =
SND_DMAENGINE_PCM_DAI_FLAG_PACK;
dev->dma_data[SNDRV_PCM_STREAM_CAPTURE].flags =
SND_DMAENGINE_PCM_DAI_FLAG_PACK;
/* BCLK ratio - use default */
dev->bclk_ratio = 0;