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ASoC: dwc: Ensure FIFOs are flushed to prevent channel swap

PATCH Superseded Andrew Jackson 2 participants 2 messages Dec 3, 2014

Subsystems (2)
Sound ASoC

v1 of 5 Superseded Latest is v5 →

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Andrew Jackson

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PATCH 5/5 ASoC: dwc: Ensure FIFOs are flushed to prevent channel swap

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 <[email protected]>
---
 sound/soc/dwc/designware_i2s.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
sound/soc/dwc/designware_i2s.c +2 -0
index 083779d..932abfd 100644
@@ -258,6 +258,7 @@ static int dw_i2s_hw_params(struct snd_pcm_substream *substream,
 	/* Iterate over set of channels - independently controlled. */
 	do {
 		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);

@@ -265,6 +266,7 @@ static int dw_i2s_hw_params(struct snd_pcm_substream *substream,
 			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);
Signature · 1 line
1.7.1
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#1 lore raw

sound/soc/dwc/designware_i2s.c static int dw_i2s_hw_params(struct snd_pcm_substream *substream, · line 261

Quoted 7 lines · Andrew Jackson

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.

sound/soc/dwc/designware_i2s.c +1 -0
 	/* Iterate over set of channels - independently controlled. */
 	do {
 		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
+			i2s_write_reg(dev->i2s_base, TXFFR, 1);

This is an example of the problem with putting fixes at the end of the series - this can't be applied without your previous change to add the support for more channels (which is a new feature).