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

[Troy Kisky]

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 at 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