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Commit a6030d71 authored by Paul Cercueil's avatar Paul Cercueil Committed by Greg Kroah-Hartman
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pwm: jz4740: Enhance precision in calculation of duty cycle 



commit 9017dc4fbd59c09463019ce494cfe36d654495a8 upstream.

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: default avatarUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: default avatarUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: default avatarPaul Cercueil <paul@crapouillou.net>
Signed-off-by: default avatarThierry Reding <thierry.reding@gmail.com>
[ukl: backport to v5.4.y and adapt commit log accordingly]
Signed-off-by: default avatarUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent d0da4be6

drivers/pwm/pwm-jz4740.c

+2 −2
Original line number Diff line number Diff line
@@ -108,8 +108,8 @@ static int jz4740_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, 
	if (prescaler == 6)

		return -EINVAL;



	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)