Re: [PATCH v11 06/12] pwm: imx27: Use 64-bit division macro and function

[Guru Das Srinagesh]

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@xxxxxxxxxxxxxx> 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.