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authorMatthias Reichl <hias@horus.com>2016-04-27 16:26:52 +0300
committerMark Brown <broonie@kernel.org>2016-04-27 19:35:53 +0300
commitbeff053c0ef6983897e3481169292e6435ef0a2d (patch)
tree16563f94c189398a71631aca60322e52a1fe1f20 /sound/soc/bcm
parentcc70666c252ce43fface105a44b6e178831660cd (diff)
downloadlinux-beff053c0ef6983897e3481169292e6435ef0a2d.tar.xz
ASoC: bcm2835: Add S16_LE support via packed DMA transfers
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>
Diffstat (limited to 'sound/soc/bcm')
-rw-r--r--sound/soc/bcm/bcm2835-i2s.c9
1 files changed, 9 insertions, 0 deletions
diff --git a/sound/soc/bcm/bcm2835-i2s.c b/sound/soc/bcm/bcm2835-i2s.c
index a0026e2d2f0a..6ba20498202e 100644
--- a/sound/soc/bcm/bcm2835-i2s.c
+++ b/sound/soc/bcm/bcm2835-i2s.c
@@ -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;