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SubjectRe: [PATCH v11 06/12] pwm: imx27: Use 64-bit division macro and function
On Fri, Mar 20, 2020 at 06:09:39PM +0100, Arnd Bergmann wrote:
> On Fri, Mar 20, 2020 at 2:42 AM Guru Das Srinagesh <gurus@codeaurora.org> wrote:
>
> > @@ -240,8 +240,7 @@ static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> >
> > period_cycles /= prescale;
> > c = (unsigned long long)period_cycles * state->duty_cycle;
> > - do_div(c, state->period);
> > - duty_cycles = c;
> > + duty_cycles = div64_u64(c, state->period);
> >
>
> This change looks fine, but I wonder if the code directly above it
>
> c = clk_get_rate(imx->clk_per);
> c *= state->period;
> do_div(c, 1000000000);
> period_cycles = c;
>
> might run into an overflow when both the clock rate and the period
> are large numbers.

Hmm. Seems to me like addressing this would be outside the scope of this
patch series.

Thank you.

Guru Das.

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