[PATCH 6/7] pwm: jz4740: Make PWM start with the active part

[Paul Cercueil]

The PWM will always start with the inactive part. To counter that,
when PWM is enabled we switch the configured polarity, and use
'period - duty + 1' as the real duty.

Signed-off-by: Paul Cercueil <p...@crapouillou.net>
---
 drivers/pwm/pwm-jz4740.c | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/drivers/pwm/pwm-jz4740.c b/drivers/pwm/pwm-jz4740.c
index 85e2110aae4f..8df898429d47 100644
--- a/drivers/pwm/pwm-jz4740.c
+++ b/drivers/pwm/pwm-jz4740.c
@@ -121,6 +121,7 @@ static int jz4740_pwm_apply(struct pwm_chip *chip, struct 
pwm_device *pwm,
                   *parent_clk = clk_get_parent(clk);
        unsigned long rate, parent_rate, period, duty;
        unsigned long long tmp;
+       bool polarity_inversed;
        int ret;
 
        parent_rate = clk_get_rate(parent_clk);
@@ -183,24 +184,27 @@ static int jz4740_pwm_apply(struct pwm_chip *chip, struct 
pwm_device *pwm,
        /* Reset counter to 0 */
        regmap_write(jz4740->map, TCU_REG_TCNTc(pwm->hwpwm), 0);
 
-       /* Set duty */
-       regmap_write(jz4740->map, TCU_REG_TDHRc(pwm->hwpwm), duty);
-
        /* Set period */
        regmap_write(jz4740->map, TCU_REG_TDFRc(pwm->hwpwm), period);
 
+       /*
+        * The PWM will always start with the inactive part. To counter that,
+        * when PWM is enabled we switch the configured polarity, and use
+        * 'period - duty + 1' as the real duty.
+        */
+
+       /* Set duty */
+       regmap_write(jz4740->map, TCU_REG_TDHRc(pwm->hwpwm), period - duty + 1);
+
        /* Set polarity */
-       switch (state->polarity) {
-       case PWM_POLARITY_NORMAL:
+       polarity_inversed = state->polarity == PWM_POLARITY_INVERSED;
+       if (!polarity_inversed ^ state->enabled)
                regmap_update_bits(jz4740->map, TCU_REG_TCSRc(pwm->hwpwm),
                                   TCU_TCSR_PWM_INITL_HIGH, 0);
-               break;
-       case PWM_POLARITY_INVERSED:
+       else
                regmap_update_bits(jz4740->map, TCU_REG_TCSRc(pwm->hwpwm),
                                   TCU_TCSR_PWM_INITL_HIGH,
                                   TCU_TCSR_PWM_INITL_HIGH);
-               break;
-       }
 
        if (state->enabled)
                jz4740_pwm_enable(chip, pwm);
-- 
2.21.0.593.g511ec345e18