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gpio: mvebu: improve pwm period calculation accuracy

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Change 'off' register value calculation from

  $off = (period - duty_cycle) * clkrate / NSEC_PER_SEC

to

  $off = (period * clkrate / NSEC_PER_SEC) - $on

That is, divide the full period value to reduce rounding error.

Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
This commit is contained in:
Baruch Siach 2021-01-20 18:16:25 +02:00 committed by Bartosz Golaszewski
parent 4bf2426103
commit aa37e27f61
1 changed files with 2 additions and 2 deletions
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4
drivers/gpio/gpio-mvebu.c
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@ -715,9 +715,9 @@ static int mvebu_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
else
on = 1;
val = (unsigned long long) mvpwm->clk_rate *
(state->period - state->duty_cycle);
val = (unsigned long long) mvpwm->clk_rate * state->period;
do_div(val, NSEC_PER_SEC);
val -= on;
if (val > UINT_MAX)
return -EINVAL;
if (val)