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

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Date:   Fri,  9 Aug 2019 14:30:30 +0200
From:   Paul Cercueil <paul@...pouillou.net>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, od@...c.me,
        linux-pwm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Paul Cercueil <paul@...pouillou.net>
Subject: [PATCH 6/7] pwm: jz4740: Make PWM start with the active part

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 <paul@...pouillou.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