[alsa-devel] [PATCH 1/2] ASoC: pcm512x: Implement the set_bclk_ratio interface

[Peter Rosin]

On 2019-01-26 14:17, Dimitris Papavasiliou wrote:
> Some boards, such as the HiFiBerry DAC+ Pro, use a pair of external
> oscillators, to generate 44.1 or 48kHz multiples and are forced to
> resort to hacks [1] in order to support 24-bit data without ending up
> with fractional dividers.  This patch allows the machine driver to use
> 32-bit frames for 24-bit data to avoid such issues.
> 
> Although the datasheet (p. 15) seems to suggest that only a handful
> of ratios are supported, it's not very explicit about it, so we allow
> the full range of values supported by the underlying register in the
> callback, to avoid needlessly rejecting potentially usable
> configurations.
> 
> [1] http://mailman.alsa-project.org/pipermail/alsa-devel/2018-December/143442.html
> 
> Signed-off-by: Dimitris Papavasiliou <dpapavas at gmail.com>
> ---
> 
> Notes:
>     This is essentially the same patch submitted previously as an RFC[1].
>     It has been split in two, in order to separate the set_bclk_ratio
>     implementation from the clocking calculation fix and some conservative
>     checking has been added to the argument of the callback.
>     
>     [1] http://mailman.alsa-project.org/pipermail/alsa-devel/2019-January/144213.html
> 
>  sound/soc/codecs/pcm512x.c | 28 ++++++++++++++++++++++++----
>  1 file changed, 24 insertions(+), 4 deletions(-)
> 
> diff --git a/sound/soc/codecs/pcm512x.c b/sound/soc/codecs/pcm512x.c
> index 6cb1653be804..b63d9392bae3 100644
> --- a/sound/soc/codecs/pcm512x.c
> +++ b/sound/soc/codecs/pcm512x.c
> @@ -55,6 +55,7 @@ struct pcm512x_priv {
>  	unsigned long overclock_dsp;
>  	int mute;
>  	struct mutex mutex;
> +	unsigned int bclk_ratio;
>  };
>  
>  /*
> @@ -915,10 +916,15 @@ static int pcm512x_set_dividers(struct snd_soc_dai *dai,
>  	int fssp;
>  	int gpio;
>  
> -	lrclk_div = snd_soc_params_to_frame_size(params);
> -	if (lrclk_div == 0) {
> -		dev_err(dev, "No LRCLK?\n");
> -		return -EINVAL;
> +	if (pcm512x->bclk_ratio > 0) {
> +		lrclk_div = pcm512x->bclk_ratio;
> +	} else {
> +		lrclk_div = snd_soc_params_to_frame_size(params);
> +
> +		if (lrclk_div == 0) {
> +			dev_err(dev, "No LRCLK?\n");
> +			return -EINVAL;
> +		}
>  	}
>  
>  	if (!pcm512x->pll_out) {
> @@ -1383,6 +1389,19 @@ static int pcm512x_set_fmt(struct snd_soc_dai *dai, unsigned int fmt)
>  	return 0;
>  }
>  
> +static int pcm512x_set_bclk_ratio(struct snd_soc_dai *dai, unsigned int ratio)
> +{
> +	struct snd_soc_component *component = dai->component;
> +	struct pcm512x_priv *pcm512x = snd_soc_component_get_drvdata(component);
> +
> +	if (ratio > 256)
> +		return -EINVAL;

ratio == 0 should also generate -EINVAL.

Cheers,
Peter

> +
> +	pcm512x->bclk_ratio = ratio;
> +
> +	return 0;
> +}
> +
>  static int pcm512x_digital_mute(struct snd_soc_dai *dai, int mute)
>  {
>  	struct snd_soc_component *component = dai->component;
> @@ -1438,6 +1457,7 @@ static const struct snd_soc_dai_ops pcm512x_dai_ops = {
>  	.hw_params = pcm512x_hw_params,
>  	.set_fmt = pcm512x_set_fmt,
>  	.digital_mute = pcm512x_digital_mute,
> +	.set_bclk_ratio = pcm512x_set_bclk_ratio,
>  };
>  
>  static struct snd_soc_dai_driver pcm512x_dai = {
>