Re: [RESEND PATCH v14 04/11] pwm: clps711x: Cast period to u32 before use as divisor

[Daniel Thompson]

On Wed, May 20, 2020 at 03:55:57PM -0700, Guru Das Srinagesh wrote:
> Since the PWM framework is switching struct pwm_args.period's datatype
> to u64, prepare for this transition by typecasting it to u32.
> 
> Also, since the dividend is still a 32-bit number, any divisor greater
> than the numerator will cause the quotient to be zero, so return 0 in
> that case to efficiently skip the division.
> 
> Signed-off-by: Guru Das Srinagesh <gurus@xxxxxxxxxxxxxx>
> ---
>  drivers/pwm/pwm-clps711x.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pwm/pwm-clps711x.c b/drivers/pwm/pwm-clps711x.c
> index 924d39a..da771b1 100644
> --- a/drivers/pwm/pwm-clps711x.c
> +++ b/drivers/pwm/pwm-clps711x.c
> @@ -43,7 +43,10 @@ static void clps711x_pwm_update_val(struct clps711x_chip *priv, u32 n, u32 v)
>  static unsigned int clps711x_get_duty(struct pwm_device *pwm, unsigned int v)
>  {
>  	/* Duty cycle 0..15 max */
> -	return DIV_ROUND_CLOSEST(v * 0xf, pwm->args.period);
> +	if (pwm->args.period > (v * 0xf))
> +		return 0;

This doesn't look right to me.

DIV_ROUND_CLOSEST() does rounded division and the short circuit doesn't
implement that.


Daniel.

> +
> +	return DIV_ROUND_CLOSEST(v * 0xf, (u32)pwm->args.period);
>  }
>  
>  static int clps711x_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
> -- 
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>