linux-kernel - [PATCH v2 2/6] ASoC: dwc: Ensure FIFOs are flushed to prevent channel swap

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Date:	Fri, 12 Dec 2014 09:25:01 +0000
From:	Andrew Jackson <andrew.jackson@....com>
To:	Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.de>
Cc:	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>,
	Rajeev Kumar <rajeevkumar.linux@...il.com>,
	Andrew Jackson <Andrew.Jackson@....com>,
	Liviu Dudau <Liviu.Dudau@....com>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Arnd Bergmann <arnd@...db.de>,
	linux-arm-kernel@...ts.infradead.org, alsa-devel@...a-project.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/6] ASoC: dwc: Ensure FIFOs are flushed to prevent channel swap

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

If the FIFOs aren't flushed, the left/right channels may be swapped:
this may occur if the FIFOs are not empty when the streams start.

Signed-off-by: Andrew Jackson <Andrew.Jackson@....com>
---
 sound/soc/dwc/designware_i2s.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/sound/soc/dwc/designware_i2s.c b/sound/soc/dwc/designware_i2s.c
index ef771ea..b9d6a25 100644
--- a/sound/soc/dwc/designware_i2s.c
+++ b/sound/soc/dwc/designware_i2s.c
@@ -228,12 +228,14 @@ static int dw_i2s_hw_params(struct snd_pcm_substream *substream,
 	i2s_disable_channels(dev, substream->stream);
 
 	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
+		i2s_write_reg(dev->i2s_base, TXFFR, 1);
 		i2s_write_reg(dev->i2s_base, TCR(ch_reg), xfer_resolution);
 		i2s_write_reg(dev->i2s_base, TFCR(ch_reg), 0x02);
 		irq = i2s_read_reg(dev->i2s_base, IMR(ch_reg));
 		i2s_write_reg(dev->i2s_base, IMR(ch_reg), irq & ~0x30);
 		i2s_write_reg(dev->i2s_base, TER(ch_reg), 1);
 	} else {
+		i2s_write_reg(dev->i2s_base, RXFFR, 1);
 		i2s_write_reg(dev->i2s_base, RCR(ch_reg), xfer_resolution);
 		i2s_write_reg(dev->i2s_base, RFCR(ch_reg), 0x07);
 		irq = i2s_read_reg(dev->i2s_base, IMR(ch_reg));
-- 
1.7.1

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