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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>
This commit is contained in:
Alexandre Belloni 2014-03-14 15:19:09 +01:00 committed by Thierry Reding
parent 8db9e29fe5
commit 916030db43
1 changed files with 1 additions and 1 deletions
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2
drivers/pwm/pwm-atmel.c
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@ -133,7 +133,7 @@ static int atmel_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
prd = div; prd = div;
div *= duty_ns; div *= duty_ns;
do_div(div, period_ns); do_div(div, period_ns);
dty = div; dty = prd - div;
ret = clk_enable(atmel_pwm->clk); ret = clk_enable(atmel_pwm->clk);
if (ret) { if (ret) {