linux-kernel - Re: [PATCH] ASoC: fsl_sai: Set SAI Channel Mode to Output Mode

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Message-ID: <20200903034018.GC4517@Asurada-Nvidia>
Date:   Wed, 2 Sep 2020 20:40:19 -0700
From:   Nicolin Chen <nicoleotsuka@...il.com>
To:     Shengjiu Wang <shengjiu.wang@....com>
Cc:     timur@...nel.org, Xiubo.Lee@...il.com, festevam@...il.com,
        broonie@...nel.org, perex@...ex.cz, tiwai@...e.com,
        alsa-devel@...a-project.org, lgirdwood@...il.com,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ASoC: fsl_sai: Set SAI Channel Mode to Output Mode

On Thu, Sep 03, 2020 at 11:09:15AM +0800, Shengjiu Wang wrote:
> Transmit data pins will output zero when slots are masked or channels
> are disabled. In CHMOD TDM mode, transmit data pins are tri-stated when
> slots are masked or channels are disabled. When data pins are tri-stated,
> there is noise on some channels when FS clock value is high and data is
> read while fsclk is transitioning from high to low.
> 
> Signed-off-by: Cosmin-Gabriel Samoila <cosmin.samoila@....com>
> Signed-off-by: Shengjiu Wang <shengjiu.wang@....com>

Acked-by: Nicolin Chen <nicoleotsuka@...il.com>

Though one nit inline:

> ---
>  sound/soc/fsl/fsl_sai.c | 12 ++++++++++--
>  sound/soc/fsl/fsl_sai.h |  2 ++
>  2 files changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/sound/soc/fsl/fsl_sai.c b/sound/soc/fsl/fsl_sai.c
> index 62c5fdb678fc..33b194a5c1dc 100644
> --- a/sound/soc/fsl/fsl_sai.c
> +++ b/sound/soc/fsl/fsl_sai.c
> @@ -486,6 +486,12 @@ static int fsl_sai_hw_params(struct snd_pcm_substream *substream,
>  
>  	val_cr4 |= FSL_SAI_CR4_FRSZ(slots);
>  
> +	/* Output Mode - data pins transmit 0 when slots are masked
> +	 * or channels are disabled
> +	 */

Coding style for multi-line comments. Yet, probably can simplify?

	/* Set to output mode to avoid tri-stated data pins */