From: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Date: Fri, 14 Mar 2014 14:19:09 +0000 (+0100)
Subject: pwm: atmel: correct CDTY calculation
X-Git-Tag: v3.15-rc1~73^2~5
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=916030db4399f9237beef480fee6b11dd83cacd5;p=thirdparty%2Fkernel%2Flinux.git

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 2d69e9c431ddc..0adc952cc4ef5 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) {