On 12/12/14 09:37, Lars-Peter Clausen wrote:

On 12/12/2014 10:25 AM, Andrew Jackson wrote:

quoted

From: Andrew Jackson <redacted>

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 <redacted>
---
  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));

This should probably go into the prepare callback. prepare is for example 
also called when recovering from a underrun/overrun. Whereas hwparams is 
only called during initial setup of the stream.

That's a good idea: thank you.  I'll rework the patch with this in mind.

	Andrew