Re: [PATCH] ASoC: meson: aiu-encoder-i2s: fix bit clock polarity

[Jerome Brunet <jbrunet@baylibre.com>]

On Tue 07 Oct 2025 at 00:12, Valerio Setti via B4 Relay <devnull+vsetti.baylibre.com@kernel.org> wrote:

> From: Valerio Setti <vsetti@baylibre.com>
>
> According to I2S specs audio data is sampled on the rising edge of the
> clock and it can change on the falling one. When operating in normal mode
> this SoC behaves the opposite so a clock polarity inversion is required
> in this case.
>
> This was tested on an OdroidC2 (Amlogic S905 SoC) board.
>
> Signed-off-by: Valerio Setti <vsetti@baylibre.com>

Reviewed-by: Jerome Brunet <jbrunet@baylibre.com>

Tested on the libretech cc s905x (GXL)

Tested-by: Jerome Brunet <jbrunet@baylibre.com>

> ---
>  sound/soc/meson/aiu-encoder-i2s.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/sound/soc/meson/aiu-encoder-i2s.c b/sound/soc/meson/aiu-encoder-i2s.c
> index a0dd914c8ed13616fbcbc0828e36418cfd255391..3b4061508c18047fe8d6f3f98061720f8ce238f2 100644
> --- a/sound/soc/meson/aiu-encoder-i2s.c
> +++ b/sound/soc/meson/aiu-encoder-i2s.c
> @@ -236,8 +236,12 @@ static int aiu_encoder_i2s_set_fmt(struct snd_soc_dai *dai, unsigned int fmt)
>  	    inv == SND_SOC_DAIFMT_IB_IF)
>  		val |= AIU_CLK_CTRL_LRCLK_INVERT;
>  
> -	if (inv == SND_SOC_DAIFMT_IB_NF ||
> -	    inv == SND_SOC_DAIFMT_IB_IF)
> +	/*
> +	 * The SoC changes data on the rising edge of the bitclock
> +	 * so an inversion of the bitclock is required in normal mode
> +	 */
> +	if (inv == SND_SOC_DAIFMT_NB_NF ||
> +	    inv == SND_SOC_DAIFMT_NB_IF)
>  		val |= AIU_CLK_CTRL_AOCLK_INVERT;
>  
>  	/* Signal skew */
> @@ -328,4 +332,3 @@ const struct snd_soc_dai_ops aiu_encoder_i2s_dai_ops = {
>  	.startup	= aiu_encoder_i2s_startup,
>  	.shutdown	= aiu_encoder_i2s_shutdown,
>  };
> -
>
> ---
> base-commit: 8f5ae30d69d7543eee0d70083daf4de8fe15d585
> change-id: 20251006-fix-i2s-polarity-d744338fa223
>
> Best regards,

-- 
Jerome