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Message-Id: <1461763613-28714-2-git-send-email-hias@horus.com>
Date: Wed, 27 Apr 2016 15:26:52 +0200
From: Matthias Reichl <hias@...us.com>
To: Liam Girdwood <lgirdwood@...il.com>,
Mark Brown <broonie@...nel.org>,
Jaroslav Kysela <perex@...ex.cz>,
Takashi Iwai <tiwai@...e.com>,
Stephen Warren <swarren@...dotorg.org>,
Lee Jones <lee@...nel.org>, Eric Anholt <eric@...olt.net>,
Martin Sperl <kernel@...tin.sperl.org>,
Luis de Bethencourt <luis@...ethencourt.com>,
alsa-devel@...a-project.org, linux-rpi-kernel@...ts.infradead.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] 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@...us.com>
---
sound/soc/bcm/bcm2835-i2s.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/sound/soc/bcm/bcm2835-i2s.c b/sound/soc/bcm/bcm2835-i2s.c
index 1c1f221..40ba01d 100644
--- a/sound/soc/bcm/bcm2835-i2s.c
+++ b/sound/soc/bcm/bcm2835-i2s.c
@@ -678,6 +678,15 @@ 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;
--
2.1.4
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