[alsa-devel] [RFC PATCH 5/5] ASoC: omap-mcbsp: Place correct constraints for streams

[Peter Ujfalusi]

On Monday 31 May 2010 11:03:26 Ujfalusi Peter (Nokia-D/Tampere) wrote:
> OMAP McBSP FIFO is word structured:
> McBSP2 has 1024 + 256 = 1280 word long buffer,
> McBSP1,3,4,5 has 128 word long buffer
> 
> This means, that the size of the FIFO
> depends on the McBSP word size configuration.
> For example on McBSP3:
> 16bit samples: size is 128 * 2 = 256 bytes
> 32bit samples: size is 128 * 4 = 512 bytes
> It is simpler to place constraint for buffer and period based on channels.
> McBSP3 as example again (16 or 32 bit samples):
> 1 channel (mono): size is 128 frames (128 words)
> 2 channels (stereo): size is 128 / 2 = 64 frames (2 * 64 words)
> 4 channels: size is 128 / 4 = 32 frames (4 * 32 words)
> 
> Use the former method to place hw_rule on buffer size, and in threshold
> mode to period size.

I meant later (second) method ;)

> 
> Signed-off-by: Peter Ujfalusi <peter.ujfalusi at nokia.com>
> ---
>  sound/soc/omap/omap-mcbsp.c |   98
> +++++++++++++++++++++++++++++++++--------- 1 files changed, 77
> insertions(+), 21 deletions(-)
> 
> diff --git a/sound/soc/omap/omap-mcbsp.c b/sound/soc/omap/omap-mcbsp.c
> index b06d8f1..d6ed761 100644
> --- a/sound/soc/omap/omap-mcbsp.c
> +++ b/sound/soc/omap/omap-mcbsp.c
> @@ -173,6 +173,52 @@ static void omap_mcbsp_set_threshold(struct
> snd_pcm_substream *substream)
> omap_mcbsp_set_rx_threshold(mcbsp_data->bus_id, words);
>  }
> 
> +static int hw_rule_bsize_by_channels(struct snd_pcm_hw_params *params,
> +				    struct snd_pcm_hw_rule *rule)
> +{
> +	struct snd_interval *bs = hw_param_interval(params,
> +					SNDRV_PCM_HW_PARAM_BUFFER_SIZE);
> +	struct snd_interval *c = hw_param_interval(params,
> +					SNDRV_PCM_HW_PARAM_CHANNELS);
> +	struct omap_mcbsp_data *mcbsp_data = rule->private;
> +	struct snd_interval frames;
> +	int size;
> +
> +	snd_interval_any(&frames);
> +	size = omap_mcbsp_get_fifo_size(mcbsp_data->bus_id);
> +
> +	frames.min = size / c->min;
> +	frames.integer = 1;
> +	return snd_interval_refine(bs, &frames);
> +
> +}
> +
> +static int hw_rule_psize_by_channels(struct snd_pcm_hw_params *params,
> +				    struct snd_pcm_hw_rule *rule)
> +{
> +	struct snd_interval *ps = hw_param_interval(params,
> +					SNDRV_PCM_HW_PARAM_PERIOD_SIZE);
> +	struct snd_interval *c = hw_param_interval(params,
> +					SNDRV_PCM_HW_PARAM_CHANNELS);
> +	struct snd_pcm_substream *substream = rule->private;
> +	struct snd_soc_pcm_runtime *rtd = substream->private_data;
> +	struct snd_soc_dai *cpu_dai = rtd->dai->cpu_dai;
> +	struct omap_mcbsp_data *mcbsp_data = to_mcbsp(cpu_dai->private_data);
> +	struct snd_interval frames;
> +	int size;
> +
> +	snd_interval_any(&frames);
> +	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
> +		size = omap_mcbsp_get_max_tx_threshold(mcbsp_data->bus_id);
> +	else
> +		size = omap_mcbsp_get_max_rx_threshold(mcbsp_data->bus_id);
> +
> +	frames.min = 8;
> +	frames.max = size / c->min;
> +	frames.integer = 1;
> +	return snd_interval_refine(ps, &frames);
> +}
> +
>  static int omap_mcbsp_dai_startup(struct snd_pcm_substream *substream,
>  				  struct snd_soc_dai *dai)
>  {
> @@ -185,33 +231,43 @@ static int omap_mcbsp_dai_startup(struct
> snd_pcm_substream *substream, if (!cpu_dai->active)
>  		err = omap_mcbsp_request(bus_id);
> 
> +	/*
> +	 * OMAP McBSP FIFO is word structured.
> +	 * McBSP2 has 1024 + 256 = 1280 word long buffer,
> +	 * McBSP1,3,4,5 has 128 word long buffer
> +	 * This means that the size of the FIFO depends on the sample format.
> +	 * For example on McBSP3:
> +	 * 16bit samples: size is 128 * 2 = 256 bytes
> +	 * 32bit samples: size is 128 * 4 = 512 bytes
> +	 * It is simpler to place constraint for buffer and period based on
> +	 * channels.
> +	 * McBSP3 as example again (16 or 32 bit samples):
> +	 * 1 channel (mono): size is 128 frames (128 words)
> +	 * 2 channels (stereo): size is 128 / 2 = 64 frames (2 * 64 words)
> +	 * 4 channels: size is 128 / 4 = 32 frames (4 * 32 words)
> +	 */
> +
> +	/*
> +	 * The first rule is for the buffer size, we should not allow smaller
> +	 * buffer than the FIFO size to avoid underruns
> +	 */
> +	snd_pcm_hw_rule_add(substream->runtime, 0, SNDRV_PCM_HW_PARAM_CHANNELS,
> +				    hw_rule_bsize_by_channels, mcbsp_data,
> +				    SNDRV_PCM_HW_PARAM_BUFFER_SIZE, -1);
> +
>  	if (cpu_is_omap343x()) {
>  		int dma_op_mode = omap_mcbsp_get_dma_op_mode(bus_id);
> -		int max_period;
> 
>  		/*
> -		 * McBSP2 in OMAP3 has 1024 * 32-bit internal audio buffer.
> -		 * Set constraint for minimum buffer size to the same than FIFO
> -		 * size in order to avoid underruns in playback startup because
> -		 * HW is keeping the DMA request active until FIFO is filled.
> +		 * In case os threshold mode, the rule will ensure, that the
> +		 * period size is not bigger than the maximum allowed threshold
> +		 * value.
>  		 */
> -		if (bus_id == 1)
> -			snd_pcm_hw_constraint_minmax(substream->runtime,
> -					SNDRV_PCM_HW_PARAM_BUFFER_BYTES,
> -					4096, UINT_MAX);
> -
> -		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
> -			max_period = omap_mcbsp_get_max_tx_threshold(bus_id);
> -		else
> -			max_period = omap_mcbsp_get_max_rx_threshold(bus_id);
> -
> -		max_period++;
> -		max_period <<= 1;
> -
>  		if (dma_op_mode == MCBSP_DMA_MODE_THRESHOLD)
> -			snd_pcm_hw_constraint_minmax(substream->runtime,
> -						SNDRV_PCM_HW_PARAM_PERIOD_BYTES,
> -						32, max_period);
> +			snd_pcm_hw_rule_add(substream->runtime, 0,
> +					SNDRV_PCM_HW_PARAM_CHANNELS,
> +					hw_rule_psize_by_channels, substream,
> +					SNDRV_PCM_HW_PARAM_PERIOD_SIZE, -1);
>  	}
> 
>  	return err;

-- 
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