linux-kernel - [PATCH 3.18 024/150] ASoC: dwc: Ensure FIFOs are flushed to prevent channel swap

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Date:	Tue, 13 Jan 2015 23:21:35 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Andrew Jackson <Andrew.Jackson@....com>,
	Mark Brown <broonie@...nel.org>
Subject: [PATCH 3.18 024/150] ASoC: dwc: Ensure FIFOs are flushed to prevent channel swap

3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andrew Jackson <Andrew.Jackson@....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@....com>
Signed-off-by: Mark Brown <broonie@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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,
 };
 


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