linux-kernel - Re: [PATCH 2/2] regulator: as3711: Fix the logic in as3711_sel

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Message-ID: <Pine.LNX.4.64.1211261445550.11501@axis700.grange>
Date:	Mon, 26 Nov 2012 14:46:25 +0100 (CET)
From:	Guennadi Liakhovetski <g.liakhovetski@....de>
To:	Axel Lin <axel.lin@...ics.com>
cc:	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Liam Girdwood <lrg@...com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] regulator: as3711: Fix the logic in as3711_sel_check

On Sat, 24 Nov 2012, Axel Lin wrote:

> Below equation means the "voltage" is the "smallest" voltage within specific
> range.
> 
> ret = DIV_ROUND_UP(min - bottom) / step;
> voltage = ret * step + bottom;
> 
> If we do try 1 down when (voltage > max), new voltage is then less than min
> voltage. Which means the new voltage is not in the requested voltage range.
> 
> This patch also includes below cleanups:
> - Use DIV_ROUND_UP
> - rename variable 'ret' to 'sel' for better readability because as3711_sel_check
>   returns the selector.
> 
> Signed-off-by: Axel Lin <axel.lin@...ics.com>

Acked-by: Guennadi Liakhovetski <g.liakhovetski@....de>

Thanks
Guennadi

> ---
>  drivers/regulator/as3711-regulator.c |   23 ++++++++---------------
>  1 file changed, 8 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/regulator/as3711-regulator.c b/drivers/regulator/as3711-regulator.c
> index 5e813b9..2f1341d 100644
> --- a/drivers/regulator/as3711-regulator.c
> +++ b/drivers/regulator/as3711-regulator.c
> @@ -93,24 +93,17 @@ static int as3711_bound_check(struct regulator_dev *rdev,
>  
>  static int as3711_sel_check(int min, int max, int bottom, int step)
>  {
> -	int ret, voltage;
> +	int sel, voltage;
>  
>  	/* Round up min, when dividing: keeps us within the range */
> -	ret = (min - bottom + step - 1) / step;
> -	voltage = ret * step + bottom;
> +	sel = DIV_ROUND_UP(min - bottom, step);
> +	voltage = sel * step + bottom;
>  	pr_debug("%s(): select %d..%d in %d+N*%d: %d\n", __func__,
> -	       min, max, bottom, step, ret);
> -	if (voltage > max) {
> -		/*
> -		 * Try 1 down. It will take us below min, but as long we stay
> -		 * above bottom, we're fine.
> -		 */
> -		ret--;
> -		voltage = ret * step + bottom;
> -		if (voltage < bottom)
> -			return -EINVAL;
> -	}
> -	return ret;
> +	       min, max, bottom, step, sel);
> +	if (voltage > max)
> +		return -EINVAL;
> +
> +	return sel;
>  }
>  
>  static int as3711_map_voltage_sd(struct regulator_dev *rdev,
> -- 
> 1.7.9.5
> 
> 
> 

---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/
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