Re: [alsa-devel] [PATCH 5/5] ASoC: DaVinci: pcm, fix underruns by using sram

Troy Kisky wrote:

Fix underruns by using dma to copy 1st to sram in a ping/pong buffer style and then copying from the sram to the ASP. This also has the advantage of tolerating very long interrupt latency on dma completion.

Signed-off-by: Troy Kisky troy.kisky@boundarydevices.com static int davinci_pcm_dma_request(struct snd_pcm_substream *substream) {

• struct snd_dma_buffer *iram_dma; struct davinci_runtime_data *prtd = substream->runtime->private_data; struct snd_soc_pcm_runtime *rtd = substream->private_data; struct davinci_pcm_dma_params *dma_data = rtd->dai->cpu_dai->dma_data;

• struct edmacc_param p_ram;
• int ret;

• int lch;

  if (!dma_data) return -ENODEV;

  prtd->params = dma_data;

• /* Request master DMA channel */
• ret = edma_alloc_channel(prtd->params->channel,

• 		  davinci_pcm_dma_irq, substream,
  

• 		  EVENTQ_0);
  

• if (ret < 0)

• return ret;
  

• prtd->asp_master_lch = ret;

• /* Request asp master DMA channel */
• lch = prtd->asp_master_lch = edma_alloc_channel(dma_data->channel,

• 	davinci_pcm_dma_irq, substream, EVENTQ_0);
  

• if (lch < 0)

• goto exit1;
  
  

• /* Request parameter RAM reload slot */
• ret = edma_alloc_slot(EDMA_CTLR(prtd->asp_master_lch), EDMA_SLOT_ANY);
• if (ret < 0) {

• edma_free_channel(prtd->asp_master_lch);
  

• return ret;
  

• }
• prtd->asp_link_lch[0] = ret;

• /* Request asp link channels */
• lch = prtd->asp_link_lch[0] = edma_alloc_slot(

• 	EDMA_CTLR(prtd->asp_master_lch), EDMA_SLOT_ANY);
  

• if (lch < 0)

• goto exit2;
  

• allocate_sram(substream, dma_data->sram_size);

This is allocated too late for the "ensure that buffer size is a multiple of period size" constraint.

I have a patch after fixing other feedback.

Troy