ARM:imx:fix pwm period value

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@linaro.org>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Cc: stable@kernel.org

diff --git a/arch/arm/plat-mxc/pwm.c b/arch/arm/plat-mxc/pwm.c
index 845de59f07edef9058a40c0afa5197d6313f8ce0..e032717f7d02c211ee8cad0d0200cec5f83974cf 100644 (file)
--- a/arch/arm/plat-mxc/pwm.c
+++ b/arch/arm/plat-mxc/pwm.c
@@ -77,6 +77,15 @@ int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
                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);