[PATCH] ASoC:pcm512x: Fix divide by zero issue.

[PATCH] ASoC:pcm512x: Fix divide by zero issue.

[Howard Mitchell]

If den=1 and pllin_rate>20MHz then den and num are adjusted to 0
causing a divide by zero error a few lines further on. Therefore
this patch correctly scales num and den such that
pllin_rate/den < 20MHz as required in the device data sheet.

Signed-off-by: Howard Mitchell <hm@hmbedded.co.uk>
---
 sound/soc/codecs/pcm512x.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sound/soc/codecs/pcm512x.c b/sound/soc/codecs/pcm512x.c
index 5301c4a..8472099 100644
--- a/sound/soc/codecs/pcm512x.c
+++ b/sound/soc/codecs/pcm512x.c
@@ -713,8 +713,8 @@ static int pcm512x_find_pll_coeff(struct snd_soc_dai *dai,
 
 	/* pllin_rate / P (or here, den) cannot be greater than 20 MHz */
 	if (pllin_rate / den > 20000000 && num < 8) {
-		num *= 20000000 / (pllin_rate / den);
-		den *= 20000000 / (pllin_rate / den);
+		num *= DIV_ROUND_UP(pllin_rate / den, 20000000);
+		den *= DIV_ROUND_UP(pllin_rate / den, 20000000);
 	}
 	dev_dbg(dev, "num / den = %lu / %lu\n", num, den);
 
-- 
1.7.9.5

Re: [PATCH] ASoC:pcm512x: Fix divide by zero issue.

[Mark Brown]

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On Fri, Mar 20, 2015 at 09:13:45PM +0000, Howard Mitchell wrote:
> If den=1 and pllin_rate>20MHz then den and num are adjusted to 0
> causing a divide by zero error a few lines further on. Therefore
> this patch correctly scales num and den such that
> pllin_rate/den < 20MHz as required in the device data sheet.

Applied, thanks.

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RE: [PATCH] ASoC:pcm512x: Fix divide by zero issue.

[Peter Rosin]

Howard Mitchell wrote;
> If den=1 and pllin_rate>20MHz then den and num are adjusted to 0
> causing a divide by zero error a few lines further on. Therefore
> this patch correctly scales num and den such that
> pllin_rate/den < 20MHz as required in the device data sheet.

Yep, the old code is plain broken and never actually ran, we have been
using 16MHz pllin_rate, and I apparently never hit this code path.

> Signed-off-by: Howard Mitchell <hm@hmbedded.co.uk>

Acked-by: Peter Rosin <peda@axentia.se>

Cheers,
Peter

> ---
>  sound/soc/codecs/pcm512x.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/sound/soc/codecs/pcm512x.c b/sound/soc/codecs/pcm512x.c
> index 5301c4a..8472099 100644
> --- a/sound/soc/codecs/pcm512x.c
> +++ b/sound/soc/codecs/pcm512x.c
> @@ -713,8 +713,8 @@ static int pcm512x_find_pll_coeff(struct snd_soc_dai
> *dai,
> 
>  	/* pllin_rate / P (or here, den) cannot be greater than 20 MHz */
>  	if (pllin_rate / den > 20000000 && num < 8) {
> -		num *= 20000000 / (pllin_rate / den);
> -		den *= 20000000 / (pllin_rate / den);
> +		num *= DIV_ROUND_UP(pllin_rate / den, 20000000);
> +		den *= DIV_ROUND_UP(pllin_rate / den, 20000000);
>  	}
>  	dev_dbg(dev, "num / den = %lu / %lu\n", num, den);
> 
> --
> 1.7.9.5