On Mon, Jan 30, 2023 at 05:32:29PM +0800, Nylon Chen wrote: > The `frac` variable represents the pulse inactive time, and the result of > this algorithm is the pulse active time. Therefore, we must reverse the > result. > > The reference is SiFive FU740-C000 Manual[0]. > > [0]: https://sifive.cdn.prismic.io/sifive/1a82e600-1f93-4f41-b2d8-86ed8b16acba_fu740-c000-manual-v1p6.pdf > > Signed-off-by: Nylon Chen <nylon.chen@xxxxxxxxxx> > --- > drivers/pwm/pwm-sifive.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/pwm/pwm-sifive.c b/drivers/pwm/pwm-sifive.c > index 62b6acc6373d..a5eda165d071 100644 > --- a/drivers/pwm/pwm-sifive.c > +++ b/drivers/pwm/pwm-sifive.c > @@ -158,6 +158,7 @@ static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm, > frac = DIV64_U64_ROUND_CLOSEST(num, state->period); > /* The hardware cannot generate a 100% duty cycle */ > frac = min(frac, (1U << PWM_SIFIVE_CMPWIDTH) - 1); > + frac = (1U << PWM_SIFIVE_CMPWIDTH) - 1 - frac; The same problem exists in pwm_sifive_get_state(), doesn't it? As fixing this is an interruptive change anyhow, this is the opportunity to align the driver to the rules tested by PWM_DEBUG. The problems I see in the driver (only checked quickly, so I might be wrong): - state->period != ddata->approx_period isn't necessarily a problem. If state->period > ddata->real_period that's fine and the driver should continue - frac = DIV64_U64_ROUND_CLOSEST(num, state->period); is wrong for two reasons: it should round down and use the real period. Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | https://www.pengutronix.de/ |
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