The release of the dma channels was being performed in prepare and there was a edma_resume call for the asp-channel only being executed on START, RESUME and PAUSE_RELEASE.
The mcasp on da850evm with ping-pong buffers enabled was exhibiting an audible glitch on every playback after the first. It was determined through trial and error that the following two changes fix this problem:
1) Move the edma_start calls from prepare to trigger and 2) reverse the order of starting the asp and ram channels.
Signed-off-by: Ben Gardiner bengardiner@nanometrics.ca Reviewed-by: Steven Faludi stevenfaludi@nanometrics.ca CC: Troy Kisky troy.kisky@boundarydevices.com
--- sound/soc/davinci/davinci-pcm.c | 13 +++++++------ 1 files changed, 7 insertions(+), 6 deletions(-)
diff --git a/sound/soc/davinci/davinci-pcm.c b/sound/soc/davinci/davinci-pcm.c index 9b5a9bf..5d9269a 100644 --- a/sound/soc/davinci/davinci-pcm.c +++ b/sound/soc/davinci/davinci-pcm.c @@ -544,6 +544,13 @@ static int davinci_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
switch (cmd) { case SNDRV_PCM_TRIGGER_START: + edma_start(prtd->asp_channel); + if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK && + prtd->ram_channel >= 0) { + /* copy 1st iram buffer */ + edma_start(prtd->ram_channel); + } + break; case SNDRV_PCM_TRIGGER_RESUME: case SNDRV_PCM_TRIGGER_PAUSE_RELEASE: edma_resume(prtd->asp_channel); @@ -582,11 +589,6 @@ static int davinci_pcm_prepare(struct snd_pcm_substream *substream) print_buf_info(prtd->asp_link[0], "asp_link[0]"); print_buf_info(prtd->asp_link[1], "asp_link[1]");
- if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) { - /* copy 1st iram buffer */ - edma_start(prtd->ram_channel); - } - edma_start(prtd->asp_channel); return 0; } prtd->period = 0; @@ -596,7 +598,6 @@ static int davinci_pcm_prepare(struct snd_pcm_substream *substream) edma_read_slot(prtd->asp_link[0], &prtd->asp_params); edma_write_slot(prtd->asp_channel, &prtd->asp_params); davinci_pcm_enqueue_dma(substream); - edma_start(prtd->asp_channel);
return 0; }