[alsa-devel] [PATCH v2 1/2] ASoC: dmaengine-pcm: Add support for querying DMA capabilities

[Vinod Koul]

On Tue, Oct 08, 2013 at 03:07:59PM +0200, Lars-Peter Clausen wrote:
> Currently each platform making use the the generic dmaengine PCM driver still
> needs to provide a custom snd_pcm_hardware struct which specifies the
> capabilities of the DMA controller, e.g. the maximum period size that can be
> supported. This patch adds code which uses the newly introduced
> dma_get_slave_caps() API to query this information from the dmaengine driver.
> The new code path will only be taken if the 'pcm_hardware' field of the
> snd_dmaengine_pcm_config struct is NULL.
> 
> The patch also introduces a new 'fifo_size' field to the
> snd_dmaengine_dai_dma_data struct which is used to initialize the
> snd_pcm_hardware 'fifo_size' field and needs to be set by the DAI driver.
> 
> Signed-off-by: Lars-Peter Clausen <lars at metafoo.de>
> 
> ---
> Changes since v1:
> 	* Use dma_get_max_seg_size() to get the maximum size of one period
> 	* Assume that a DMA engine driver is able to support an infinite number of
> 	  periods
> 	* Increase min_period_bytes from 16 to 256.
> ---
>  include/sound/dmaengine_pcm.h         |  2 ++
>  sound/soc/soc-generic-dmaengine-pcm.c | 55 ++++++++++++++++++++++++++++-------
>  2 files changed, 47 insertions(+), 10 deletions(-)
> 
> diff --git a/include/sound/dmaengine_pcm.h b/include/sound/dmaengine_pcm.h
> index f11c35c..83b2c3e 100644
> --- a/include/sound/dmaengine_pcm.h
> +++ b/include/sound/dmaengine_pcm.h
> @@ -61,6 +61,7 @@ struct dma_chan *snd_dmaengine_pcm_get_chan(struct snd_pcm_substream *substream)
>   * @slave_id: Slave requester id for the DMA channel.
>   * @filter_data: Custom DMA channel filter data, this will usually be used when
>   * requesting the DMA channel.
> + * @fifo_size: FIFO size of the DAI controller in bytes
is this supposed to be DMA FIFO or I2S FIFO? 

And second question for Takakshi or Mark. I see that this value ends up in
usermode, what is the intented usage of this?

>   */
>  struct snd_dmaengine_dai_dma_data {
>  	dma_addr_t addr;
> @@ -68,6 +69,7 @@ struct snd_dmaengine_dai_dma_data {
>  	u32 maxburst;
>  	unsigned int slave_id;
>  	void *filter_data;
> +	unsigned int fifo_size;
>  };
>  
>  void snd_dmaengine_pcm_set_config_from_dai_data(
> diff --git a/sound/soc/soc-generic-dmaengine-pcm.c b/sound/soc/soc-generic-dmaengine-pcm.c
> index e29ec3c..c39e19e 100644
> --- a/sound/soc/soc-generic-dmaengine-pcm.c
> +++ b/sound/soc/soc-generic-dmaengine-pcm.c
> @@ -36,6 +36,15 @@ static struct dmaengine_pcm *soc_platform_to_pcm(struct snd_soc_platform *p)
>  	return container_of(p, struct dmaengine_pcm, platform);
>  }
>  
> +static struct device *dmaengine_dma_dev(struct dmaengine_pcm *pcm,
> +	struct snd_pcm_substream *substream)
> +{
> +	if (!pcm->chan[substream->stream])
> +		return NULL;
> +
> +	return pcm->chan[substream->stream]->device->dev;
> +}
> +
>  /**
>   * snd_dmaengine_pcm_prepare_slave_config() - Generic prepare_slave_config callback
>   * @substream: PCM substream
> @@ -92,28 +101,54 @@ static int dmaengine_pcm_hw_params(struct snd_pcm_substream *substream,
>  	return snd_pcm_lib_malloc_pages(substream, params_buffer_bytes(params));
>  }
>  
> -static int dmaengine_pcm_open(struct snd_pcm_substream *substream)
> +static int dmaengine_pcm_set_runtime_hwparams(struct snd_pcm_substream *substream)
>  {
>  	struct snd_soc_pcm_runtime *rtd = substream->private_data;
>  	struct dmaengine_pcm *pcm = soc_platform_to_pcm(rtd->platform);
> +	struct device *dma_dev = dmaengine_dma_dev(pcm, substream);
>  	struct dma_chan *chan = pcm->chan[substream->stream];
> +	struct snd_dmaengine_dai_dma_data *dma_data;
> +	struct dma_slave_caps dma_caps;
> +	struct snd_pcm_hardware hw;
>  	int ret;
>  
> -	ret = snd_soc_set_runtime_hwparams(substream,
> +	if (pcm->config->pcm_hardware)
> +		return snd_soc_set_runtime_hwparams(substream,
>  				pcm->config->pcm_hardware);
> -	if (ret)
> -		return ret;
>  
> -	return snd_dmaengine_pcm_open(substream, chan);
> +	dma_data = snd_soc_dai_get_dma_data(rtd->cpu_dai, substream);
> +
> +	memset(&hw, 0, sizeof(hw));
> +	hw.info = SNDRV_PCM_INFO_MMAP | SNDRV_PCM_INFO_MMAP_VALID |
> +			SNDRV_PCM_INFO_INTERLEAVED;
> +	hw.periods_min = 2;
> +	hw.periods_max = UINT_MAX;
> +	hw.period_bytes_min = 256;
> +	hw.period_bytes_max = dma_get_max_seg_size(dma_dev);
I think you should check if the driver has set this, if not goto some default

-- 
~Vinod