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

1 files changed, 9 insertions, 0 deletions

diff --git a/arch/arm/plat-mxc/pwm.c b/arch/arm/plat-mxc/pwm.c
index 845de59f07ed..e032717f7d02 100644
--- 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);