pwm: atmel: correct CDTY calculation

From the datasheet, the actual duty cycle is:

	(period - (1 / clk) * CDTY) / period

This actually correct the polarity of the PWM and solves the issue that
pwm-leds exhibits: when setting a duty cycle of 0 and then disabling a
channel, the level was wrong (1 when the polarity was normal and 0 when
the polarity was inversed).

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

diff --git a/drivers/pwm/pwm-atmel.c b/drivers/pwm/pwm-atmel.c
index 2d69e9c431ddc17d25e7674a35a54bfa37f5b6f8..0adc952cc4ef5e95d8a5bd0fa0a680663150b7e8 100644 (file)
--- a/drivers/pwm/pwm-atmel.c
+++ b/drivers/pwm/pwm-atmel.c
@@ -133,7 +133,7 @@ static int atmel_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
        prd = div;
        div *= duty_ns;
        do_div(div, period_ns);
-       dty = div;
+       dty = prd - div;
 
        ret = clk_enable(atmel_pwm->clk);
        if (ret) {