linux-kernel - RE: [PATCH v8 01/12] clk: pwm: Use 64-bit division function

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Message-ID: <7506bc2972324fd286dac6327ec73a3a@AcuMS.aculab.com>
Date:   Wed, 11 Mar 2020 16:58:24 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Guru Das Srinagesh' <gurus@...eaurora.org>,
        "linux-pwm@...r.kernel.org" <linux-pwm@...r.kernel.org>
CC:     Thierry Reding <thierry.reding@...il.com>,
        Uwe Kleine-König <uwe@...ine-koenig.org>,
        "Subbaraman Narayanamurthy" <subbaram@...eaurora.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>
Subject: RE: [PATCH v8 01/12] clk: pwm: Use 64-bit division function

From: Guru Das Srinagesh
> Sent: 11 March 2020 01:41
> 
> Since the PWM framework is switching struct pwm_args.period's datatype
> to u64, prepare for this transition by using div64_u64 to handle a
> 64-bit divisor.
> 
> Cc: Michael Turquette <mturquette@...libre.com>
> Cc: Stephen Boyd <sboyd@...nel.org>
> Cc: linux-clk@...r.kernel.org
> 
> Signed-off-by: Guru Das Srinagesh <gurus@...eaurora.org>
> ---
>  drivers/clk/clk-pwm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/clk/clk-pwm.c b/drivers/clk/clk-pwm.c
> index 87fe0b0e..7b1f7a0 100644
> --- a/drivers/clk/clk-pwm.c
> +++ b/drivers/clk/clk-pwm.c
> @@ -89,7 +89,7 @@ static int clk_pwm_probe(struct platform_device *pdev)
>  	}
> 
>  	if (of_property_read_u32(node, "clock-frequency", &clk_pwm->fixed_rate))
> -		clk_pwm->fixed_rate = NSEC_PER_SEC / pargs.period;
> +		clk_pwm->fixed_rate = div64_u64(NSEC_PER_SEC, pargs.period);

That cannot be needed, a 32 bit division is fine.
More interesting would be whether pargs.period is sane (eg not zero).
I'd assign pargs.period to an 'unsigned int' variable
prior to the division (I hate casts - been bitten by them in the past.).

> 
>  	if (pargs.period != NSEC_PER_SEC / clk_pwm->fixed_rate &&
>  	    pargs.period != DIV_ROUND_UP(NSEC_PER_SEC, clk_pwm->fixed_rate)) {
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project

	David

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