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: f6b8a5700057 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/pwm/pwm-jz4740.c b/drivers/pwm/pwm-jz4740.c
index 3cd5c054ad9aff82c7f8b7465419d9682fbce753..4fe9d99ac9a9003f75d215671c5783a3c441cd9a 100644 (file)
--- a/drivers/pwm/pwm-jz4740.c
+++ b/drivers/pwm/pwm-jz4740.c
@@ -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)