Commit 9017dc4f authored May 27, 2020 by Paul Cercueil Committed by Thierry Reding Jun 02, 2020

pwm: jz4740: Enhance precision in calculation of duty cycle



Calculating the hardware value for the duty from the hardware value of
the period resulted in a precision loss versus calculating it from the
clock rate directly.

(Also remove a cast that doesn't really need to be here)

Fixes: f6b8a570 ("pwm: Add Ingenic JZ4740 support")
Cc: <stable@vger.kernel.org>
Suggested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

parent b48d49e0

drivers/pwm/pwm-jz4740.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -158,11 +158,11 @@ static int jz4740_pwm_apply(struct pwm_chip chip, struct pwm_device pwm,
		/* Calculate period value */
		tmp = (unsigned long long)rate * state->period;
		do_div(tmp, NSEC_PER_SEC);
		period = (unsigned long)tmp;
		period = tmp;

		/* Calculate duty value */
		tmp = (unsigned long long)period * state->duty_cycle;
		do_div(tmp, state->period);
		tmp = (unsigned long long)rate * state->duty_cycle;
		do_div(tmp, NSEC_PER_SEC);
		duty = period - tmp;

		if (duty >= period)

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