| Message ID | 0cd077886d37699bdf0a20295fd8ee422e5285b5.1609849176.git.baruch@tkos.co.il (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | gpio: mvebu: Armada 8K/7K PWM support | expand |
On Tue, Jan 05, 2021 at 02:42:28PM +0200, Baruch Siach wrote: > The period is the sum of on and off values. > > Reported-by: Russell King <linux@armlinux.org.uk> > Fixes: 757642f9a584e ("gpio: mvebu: Add limited PWM support") > Signed-off-by: Baruch Siach <baruch@tkos.co.il> > --- > drivers/gpio/gpio-mvebu.c | 16 ++++++---------- > 1 file changed, 6 insertions(+), 10 deletions(-) > > diff --git a/drivers/gpio/gpio-mvebu.c b/drivers/gpio/gpio-mvebu.c > index 672681a976f5..ac7cb6d3702e 100644 > --- a/drivers/gpio/gpio-mvebu.c > +++ b/drivers/gpio/gpio-mvebu.c > @@ -679,17 +679,13 @@ static void mvebu_pwm_get_state(struct pwm_chip *chip, > regmap_read(mvpwm->regs, mvebu_pwmreg_blink_off_duration(mvpwm), &u); > val = (unsigned long long) u * NSEC_PER_SEC; > do_div(val, mvpwm->clk_rate); > - if (val < state->duty_cycle) { > + val += state->duty_cycle; > + if (val > UINT_MAX) > + state->period = UINT_MAX; > + else if (val) > + state->period = val; > + else > state->period = 1; Are you sure this is the correct solution? Aren't you introducing rounding errors? The hardware will count to (on + off) clock ticks, so the right way to convert that is to add the two together and then convert to nanoseconds, which may result in a single rounding error. If you convert each individually to nanoseconds, then you can end up with two sets of rounding errors.
diff --git a/drivers/gpio/gpio-mvebu.c b/drivers/gpio/gpio-mvebu.c index 672681a976f5..ac7cb6d3702e 100644 --- a/drivers/gpio/gpio-mvebu.c +++ b/drivers/gpio/gpio-mvebu.c @@ -679,17 +679,13 @@ static void mvebu_pwm_get_state(struct pwm_chip *chip, regmap_read(mvpwm->regs, mvebu_pwmreg_blink_off_duration(mvpwm), &u); val = (unsigned long long) u * NSEC_PER_SEC; do_div(val, mvpwm->clk_rate); - if (val < state->duty_cycle) { + val += state->duty_cycle; + if (val > UINT_MAX) + state->period = UINT_MAX; + else if (val) + state->period = val; + else state->period = 1; - } else { - val -= state->duty_cycle; - if (val > UINT_MAX) - state->period = UINT_MAX; - else if (val) - state->period = val; - else - state->period = 1; - } regmap_read(mvchip->regs, GPIO_BLINK_EN_OFF + mvchip->offset, &u); if (u)
The period is the sum of on and off values. Reported-by: Russell King <linux@armlinux.org.uk> Fixes: 757642f9a584e ("gpio: mvebu: Add limited PWM support") Signed-off-by: Baruch Siach <baruch@tkos.co.il> --- drivers/gpio/gpio-mvebu.c | 16 ++++++---------- 1 file changed, 6 insertions(+), 10 deletions(-)