linux-kernel - Re: [PATCH] ASoC: fsl_esai: Fix divisor calculation failure at lower ratio

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Date:   Mon, 9 Apr 2018 23:43:02 +0200
From:   Marek Vasut <marex@...x.de>
To:     Nicolin Chen <nicoleotsuka@...il.com>, broonie@...nel.org
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        alsa-devel@...a-project.org, tiwai@...e.com, perex@...ex.cz,
        lgirdwood@...il.com, fabio.estevam@....com
Subject: Re: [PATCH] ASoC: fsl_esai: Fix divisor calculation failure at lower
 ratio

On 04/09/2018 01:57 AM, Nicolin Chen wrote:
> When the desired ratio is less than 256, the savesub (tolerance)
> in the calculation would become 0. This will then fail the loop-
> search immediately without reporting any errors.
> 
> But if the ratio is smaller enough, there is no need to calculate
> the tolerance because PM divisor alone is enough to get the ratio.
> 
> So a simple fix could be just to set PM directly instead of going
> into the loop-search.
> 
> Reported-by: Marek Vasut <marex@...x.de>
> Signed-off-by: Nicolin Chen <nicoleotsuka@...il.com>
> Cc: Marek Vasut <marex@...x.de>

On i.MX6Q with TI PCM1808
Tested-by: Marek Vasut <marex@...x.de>

> ---
>  sound/soc/fsl/fsl_esai.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/sound/soc/fsl/fsl_esai.c b/sound/soc/fsl/fsl_esai.c
> index 40a7004..da8fd98 100644
> --- a/sound/soc/fsl/fsl_esai.c
> +++ b/sound/soc/fsl/fsl_esai.c
> @@ -144,6 +144,13 @@ static int fsl_esai_divisor_cal(struct snd_soc_dai *dai, bool tx, u32 ratio,
>  
>  	psr = ratio <= 256 * maxfp ? ESAI_xCCR_xPSR_BYPASS : ESAI_xCCR_xPSR_DIV8;
>  
> +	/* Do not loop-search if PM (1 ~ 256) alone can serve the ratio */
> +	if (ratio <= 256) {
> +		pm = ratio;
> +		fp = 1;
> +		goto out;
> +	}
> +
>  	/* Set the max fluctuation -- 0.1% of the max devisor */
>  	savesub = (psr ? 1 : 8)  * 256 * maxfp / 1000;
>  
> 


-- 
Best regards,
Marek Vasut