On Thu, May 21, 2020 at 11:19:34AM +0100, Daniel Thompson wrote: > 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 <[email protected]> > > --- > > 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.
My initial patch [1] was to simply use DIV64_U64_ROUND_CLOSEST(), but I got review feedback to add a short-circuit (same thread, [2]). I feel like I should skip the short-circuiting and type casting and simply just use DIV64_U64_ROUND_CLOSEST() - what do you think? [1] https://lore.kernel.org/lkml/587f9ccae68ad7e1ce97fa8da6037292af1a5095.1584473399.git.gu...@codeaurora.org/ [2] https://lore.kernel.org/lkml/cak8p3a2hi_aorc3g7qkth4e_y1jzrbbdhwub3ypzm10fwmu...@mail.gmail.com/
