Messages in this thread Patch in this message | | | From | Alexandre Belloni <> | Subject | [PATCH 2/2] PWM: atmel: correct CDTY calculation | Date | Fri, 14 Mar 2014 15:19:09 +0100 |
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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> --- drivers/pwm/pwm-atmel.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/pwm/pwm-atmel.c b/drivers/pwm/pwm-atmel.c index 2d69e9c431dd..0adc952cc4ef 100644 --- 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) { -- 1.8.3.2
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