From a6030d71e62d3e0e270bf3b7fb48d32a636732db Mon Sep 17 00:00:00 2001 From: Paul Cercueil Date: Wed, 27 May 2020 13:52:23 +0200 Subject: [PATCH] pwm: jz4740: Enhance precision in calculation of duty cycle MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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: f6b8a5700057 ("pwm: Add Ingenic JZ4740 support") Cc: Suggested-by: Uwe Kleine-König Reviewed-by: Uwe Kleine-König Signed-off-by: Paul Cercueil Signed-off-by: Thierry Reding [ukl: backport to v5.4.y and adapt commit log accordingly] Signed-off-by: Uwe Kleine-König Signed-off-by: Greg Kroah-Hartman --- drivers/pwm/pwm-jz4740.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/pwm/pwm-jz4740.c b/drivers/pwm/pwm-jz4740.c index 9d78cc2..d0f5c69 100644 --- a/drivers/pwm/pwm-jz4740.c +++ b/drivers/pwm/pwm-jz4740.c @@ -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) -- 2.7.4