linux-kernel - Re: [PATCH v8 03/12] hwmon: pwm-fan: Use 64-bit division macro

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Message-ID: <20200311150816.GA10018@roeck-us.net>
Date:   Wed, 11 Mar 2020 08:08:16 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Guru Das Srinagesh <gurus@...eaurora.org>
Cc:     linux-pwm@...r.kernel.org,
        Thierry Reding <thierry.reding@...il.com>,
        Uwe Kleine-König <uwe@...ine-koenig.org>,
        Subbaraman Narayanamurthy <subbaram@...eaurora.org>,
        linux-kernel@...r.kernel.org, Kamil Debski <kamil@...as.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Jean Delvare <jdelvare@...e.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>, linux-hwmon@...r.kernel.org
Subject: Re: [PATCH v8 03/12] hwmon: pwm-fan: Use 64-bit division macro

On Tue, Mar 10, 2020 at 06:41:12PM -0700, Guru Das Srinagesh wrote:
> Since the PWM framework is switching struct pwm_args.period's datatype
> to u64, prepare for this transition by using DIV_ROUND_UP_ULL to handle
> a 64-bit dividend.
> 
> Cc: Kamil Debski <kamil@...as.org>
> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
> Cc: Jean Delvare <jdelvare@...e.com>
> Cc: Guenter Roeck <linux@...ck-us.net>
> Cc: Liam Girdwood <lgirdwood@...il.com>
> Cc: Mark Brown <broonie@...nel.org>
> Cc: linux-hwmon@...r.kernel.org
> 
> Signed-off-by: Guru Das Srinagesh <gurus@...eaurora.org>

Not sure if I entirely buy the use case, but then the performance
impact is minimal, at least for this driver, so

Acked-by: Guenter Roeck <linux@...ck-us.net>

Guenter

> ---
>  drivers/hwmon/pwm-fan.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
> index 42ffd2e..283423a 100644
> --- a/drivers/hwmon/pwm-fan.c
> +++ b/drivers/hwmon/pwm-fan.c
> @@ -437,7 +437,7 @@ static int pwm_fan_resume(struct device *dev)
>  		return 0;
>  
>  	pwm_get_args(ctx->pwm, &pargs);
> -	duty = DIV_ROUND_UP(ctx->pwm_value * (pargs.period - 1), MAX_PWM);
> +	duty = DIV_ROUND_UP_ULL(ctx->pwm_value * (pargs.period - 1), MAX_PWM);
>  	ret = pwm_config(ctx->pwm, duty, pargs.period);
>  	if (ret)
>  		return ret;
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>