[alsa-devel] [PATCH V2 2/2] ASoC: SAMSUNG: Add WM8994 PCM Machine driver

[Mark Brown]

On Thu, Apr 28, 2011 at 10:32:52AM +0900, Sangbeom Kim wrote:

> +	/* Set the codec DAI configuration */
> +	ret = snd_soc_dai_set_fmt(codec_dai, SND_SOC_DAIFMT_DSP_B
> +				| SND_SOC_DAIFMT_IB_NF
> +				| SND_SOC_DAIFMT_CBS_CFS);
> +	if (ret < 0)
> +		return ret;

> +	/* Set the cpu DAI configuration */
> +	ret = snd_soc_dai_set_fmt(cpu_dai, SND_SOC_DAIFMT_DSP_B
> +				| SND_SOC_DAIFMT_IB_NF
> +				| SND_SOC_DAIFMT_CBS_CFS);
> +	if (ret < 0)
> +		return ret;

> +	ret = snd_soc_dai_set_sysclk(codec_dai, WM8994_SYSCLK_FLL1,
> +					mclk_freq, SND_SOC_CLOCK_IN);
> +	if (ret < 0)
> +		return ret;

For optimal performance the CODEC AIFnCLK needs to be synchronous with
the audio interface clocks.  This means that you should either clock the
FLL from the CPU BCLK or you should make the CODEC master for the AIF.

> +static struct snd_soc_ops smdk_wm8994_pcm_ops = {
> +	.hw_params = smdk_wm8994_pcm_hw_params,
> +};

Note also that the FLL is never stopped in this system - this will not
be optimally power efficient.  It probably doesn't matter too much on
the reference board itself but on systems derived from it it would be an
issue.

> +static struct snd_soc_dai_link smdk_dai[] = {

> +static struct snd_soc_card smdk_pcm = {
> +	.name = "SMDK-PCM",
> +	.dai_link = smdk_dai,
> +	.num_links = 1,

Since the links are in an array using ARRAY_SIZE() would be better.

> +static int __init smdk_audio_init(void)
> +{
> +	return platform_driver_register(&snd_smdk_driver);
> +}
> +
> +module_init(smdk_audio_init);

Random blank line there.