On Thu, May 21, 2020 at 01:25:25PM -0700, Guru Das Srinagesh wrote: > 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?
A trivial review of pwm-clps711x.c suggests that the period is always 32-bit anyway so why not just throw away the short circuit entirely and replace with a comment saying that CLPS711X has a hard coded period that is always >1000000000 ? Daniel.
