Commit aa37e27f authored Jan 20, 2021 by Baruch Siach Committed by Bartosz Golaszewski Feb 15, 2021

gpio: mvebu: improve pwm period calculation accuracy



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>

parent 4bf24261

drivers/gpio/gpio-mvebu.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -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)