linux-kernel - Re: [PATCH v2] ASoC: wm8524: enable constraints when sysclk is configured.

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Message-ID: <aFEtiKQ5RvvZEt5x@opensource.cirrus.com>
Date: Tue, 17 Jun 2025 09:55:36 +0100
From: Charles Keepax <ckeepax@...nsource.cirrus.com>
To: Shengjiu Wang <shengjiu.wang@....com>
Cc: lgirdwood@...il.com, broonie@...nel.org, perex@...ex.cz, tiwai@...e.com,
        patches@...nsource.cirrus.com, linux-sound@...r.kernel.org,
        linux-kernel@...r.kernel.org, shengjiu.wang@...il.com
Subject: Re: [PATCH v2] ASoC: wm8524: enable constraints when sysclk is
 configured.

On Tue, Jun 17, 2025 at 03:18:33PM +0800, Shengjiu Wang wrote:
> In some cases, the sysclk won't be configured on init, and sysclk can be
> changed in hw_params() according to different sample rate, for example,
> for 44kHz sample rate, the sysclk is 11.2896MHz, for 48kHz sample rate,
> the sysclk is 12.288MHz.
> 
> In order to support the above case, only enable constraints when sysclk
> is configured.
> 
> Signed-off-by: Shengjiu Wang <shengjiu.wang@....com>
> ---
> changes in v2
> - Don't remove constraints, but only enable constraints when sysclk
>   is configured.
> 
>  sound/soc/codecs/wm8524.c | 17 +++++++----------
>  1 file changed, 7 insertions(+), 10 deletions(-)
> 
> diff --git a/sound/soc/codecs/wm8524.c b/sound/soc/codecs/wm8524.c
> index 403e513f3fa8..5d8fb45db272 100644
> --- a/sound/soc/codecs/wm8524.c
> +++ b/sound/soc/codecs/wm8524.c
> @@ -63,17 +63,12 @@ static int wm8524_startup(struct snd_pcm_substream *substream,
>  	struct wm8524_priv *wm8524 = snd_soc_component_get_drvdata(component);
>  
>  	/* The set of sample rates that can be supported depends on the
> -	 * MCLK supplied to the CODEC - enforce this.
> +	 * MCLK supplied to the CODEC.
>  	 */
> -	if (!wm8524->sysclk) {
> -		dev_err(component->dev,
> -			"No MCLK configured, call set_sysclk() on init\n");
> -		return -EINVAL;
> -	}
> -
> -	snd_pcm_hw_constraint_list(substream->runtime, 0,
> -				   SNDRV_PCM_HW_PARAM_RATE,
> -				   &wm8524->rate_constraint);
> +	if (wm8524->sysclk)
> +		snd_pcm_hw_constraint_list(substream->runtime, 0,
> +					   SNDRV_PCM_HW_PARAM_RATE,
> +					   &wm8524->rate_constraint);
>  
>  	gpiod_set_value_cansleep(wm8524->mute, 1);
>  

If we are allow the clock to be set at hw_params time, we
should probably also double check the rates in hw_params and
return an error if its not supported.

> @@ -98,6 +93,8 @@ static int wm8524_set_dai_sysclk(struct snd_soc_dai *codec_dai,
>  	int i, j = 0;
>  
>  	wm8524->sysclk = freq;
> +	if (!wm8524->sysclk)
> +		return 0;
>  
>  	wm8524->rate_constraint.count = 0;
>  	for (i = 0; i < ARRAY_SIZE(lrclk_ratios); i++) {

We probably should clear rate_constraint.count in the clearing
sysclk case, and we should probably also check if the DAI is
active. The user shoudln't be allowed to change clock there is
audio already happening.

Thanks,
Charles