linux-kernel - Re: [PATCH 1/1] fixing pwm-mxs period divider computation

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Message-ID: <20150218121123.GB18576@ulmo>
Date:	Wed, 18 Feb 2015 13:11:24 +0100
From:	Thierry Reding <thierry.reding@...il.com>
To:	Gaetan Hug <ghug@...uct.be>
Cc:	linux-pwm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Shawn Guo <shawn.guo@...aro.org>,
	Fabio Estevam <fabio.estevam@...escale.com>
Subject: Re: [PATCH 1/1] fixing pwm-mxs period divider computation

On Wed, Feb 18, 2015 at 09:18:56AM +0100, Gaetan Hug wrote:
> ---
>  drivers/pwm/pwm-mxs.c |    7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)

Adding Shawn and Fabio, hence quoting the full patch.

> diff --git a/drivers/pwm/pwm-mxs.c b/drivers/pwm/pwm-mxs.c
> index f75ecb0..bbb2f8a 100644
> --- a/drivers/pwm/pwm-mxs.c
> +++ b/drivers/pwm/pwm-mxs.c
> @@ -52,15 +52,18 @@ static int mxs_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
>  	unsigned long rate;
>  	unsigned long long c;
>  
> +    unsigned const int cdiv[PERIOD_CDIV_MAX] = {1, 2, 4, 8, 16, 64, 256, 1024};

This could prbably be static const and could be in file scope rather
than in this function.

Thierry

> +
>  	rate = clk_get_rate(mxs->clk);
> +
>  	while (1) {
> -		c = rate / (1 << div);
> +		c = rate / cdiv[div];
>  		c = c * period_ns;
>  		do_div(c, 1000000000);
>  		if (c < PERIOD_PERIOD_MAX)
>  			break;
>  		div++;
> -		if (div > PERIOD_CDIV_MAX)
> +		if (div >= PERIOD_CDIV_MAX)
>  			return -EINVAL;
>  	}
>  
> -- 
> 1.7.10.4
> 

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