linux-kernel - [5/7] ARM:imx:fix pwm period value

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Message-Id: <20120103220242.485129929@clark.kroah.org>
Date:	Tue, 03 Jan 2012 14:01:35 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Jason Chen <jason.chen@...aro.org>,
	Sascha Hauer <s.hauer@...gutronix.de>
Subject: [5/7] ARM:imx:fix pwm period value

2.6.32-longterm review patch.  If anyone has any objections, please let me know.

------------------

From: Jason Chen <jason.chen@...aro.org>

commit 5776ac2eb33164c77cdb4d2b48feee15616eaba3 upstream.

According to imx pwm RM, the real period value should be
PERIOD value in PWMPR plus 2.

PWMO (Hz) = PCLK(Hz) / (period +2)

Signed-off-by: Jason Chen <jason.chen@...aro.org>
Signed-off-by: Sascha Hauer <s.hauer@...gutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 arch/arm/plat-mxc/pwm.c |    9 +++++++++
 1 file changed, 9 insertions(+)

--- a/arch/arm/plat-mxc/pwm.c
+++ b/arch/arm/plat-mxc/pwm.c
@@ -76,6 +76,15 @@ int pwm_config(struct pwm_device *pwm, i
 		do_div(c, period_ns);
 		duty_cycles = c;
 
+		/*
+		 * according to imx pwm RM, the real period value should be
+		 * PERIOD value in PWMPR plus 2.
+		 */
+		if (period_cycles > 2)
+			period_cycles -= 2;
+		else
+			period_cycles = 0;
+
 		writel(duty_cycles, pwm->mmio_base + MX3_PWMSAR);
 		writel(period_cycles, pwm->mmio_base + MX3_PWMPR);
 


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