[PATCH 3.10 10/44] ASoC: dwc: Ensure FIFOs are flushed to prevent channel swap

Greg Kroah-Hartman
2015-01-14T07:49:48Z

From: Andrew Jackson <Andrew.Jackson@arm.com>

commit 3475c3d034d7f276a474c8bd53f44b48c8bf669d upstream.

Flush the FIFOs when the stream is prepared for use. This avoids
an inadvertent swapping of the left/right channels if the FIFOs are
not empty at startup.

Signed-off-by: Andrew Jackson <Andrew.Jackson@arm.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
sound/soc/dwc/designware_i2s.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)

--- a/sound/soc/dwc/designware_i2s.c
+++ b/sound/soc/dwc/designware_i2s.c
@@ -263,6 +263,19 @@ static void dw_i2s_shutdown(struct snd_p
snd_soc_dai_set_dma_data(dai, substream, NULL);
}

+static int dw_i2s_prepare(struct snd_pcm_substream *substream,
+ struct snd_soc_dai *dai)
+{
+ struct dw_i2s_dev *dev = snd_soc_dai_get_drvdata(dai);
+
+ if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+ i2s_write_reg(dev->i2s_base, TXFFR, 1);
+ else
+ i2s_write_reg(dev->i2s_base, RXFFR, 1);
+
+ return 0;
+}
+
static int dw_i2s_trigger(struct snd_pcm_substream *substream,
int cmd, struct snd_soc_dai *dai)
{
@@ -294,6 +307,7 @@ static struct snd_soc_dai_ops dw_i2s_dai
.startup = dw_i2s_startup,
.shutdown = dw_i2s_shutdown,
.hw_params = dw_i2s_hw_params,
+ .prepare = dw_i2s_prepare,
.trigger = dw_i2s_trigger,
};