linux-kernel - [PATCH 1/2] PWM: atmel: fix incorrect CDTY value after enabling

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Date:	Mon, 25 May 2015 15:19:55 +0200
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Thierry Reding <thierry.reding@...il.com>
Cc:	Nicolas Ferre <nicolas.ferre@...el.com>, linux-pwm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
Subject: [PATCH 1/2] PWM: atmel: fix incorrect CDTY value after enabling

CUPD is not flushed before enabling the channel so it will update CDTY/CPRD just
after one period. So we always set CUPD, even when the channel is not enabled.

Signed-off-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
---
 drivers/pwm/pwm-atmel.c | 35 ++++++++++++++++++-----------------
 1 file changed, 18 insertions(+), 17 deletions(-)

diff --git a/drivers/pwm/pwm-atmel.c b/drivers/pwm/pwm-atmel.c
index d3c22de9ee47..89f9ca41d9af 100644
--- a/drivers/pwm/pwm-atmel.c
+++ b/drivers/pwm/pwm-atmel.c
@@ -155,24 +155,25 @@ static void atmel_pwm_config_v1(struct pwm_chip *chip, struct pwm_device *pwm,
 	struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
 	unsigned int val;
 
-	if (test_bit(PWMF_ENABLED, &pwm->flags)) {
-		/*
-		 * If the PWM channel is enabled, using the update register,
-		 * it needs to set bit 10 of CMR to 0
-		 */
-		atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWMV1_CUPD, dty);
 
-		val = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm, PWM_CMR);
-		val &= ~PWM_CMR_UPD_CDTY;
-		atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWM_CMR, val);
-	} else {
-		/*
-		 * If the PWM channel is disabled, write value to duty and
-		 * period registers directly.
-		 */
-		atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWMV1_CDTY, dty);
-		atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWMV1_CPRD, prd);
-	}
+	atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWMV1_CUPD, dty);
+
+	val = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm, PWM_CMR);
+	val &= ~PWM_CMR_UPD_CDTY;
+	atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWM_CMR, val);
+
+	/*
+	 * If the PWM channel is enabled, only update CDTY by using the update
+	 * register, it needs to set bit 10 of CMR to 0
+	 */
+	if (test_bit(PWMF_ENABLED, &pwm->flags))
+		return;
+	/*
+	 * If the PWM channel is disabled, write value to duty and period
+	 * registers directly.
+	 */
+	atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWMV1_CDTY, dty);
+	atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWMV1_CPRD, prd);
 }
 
 static void atmel_pwm_config_v2(struct pwm_chip *chip, struct pwm_device *pwm,
-- 
2.1.4

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