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From:   Clemens Gruber <clemens.gruber@pqgruber.com>
To:     linux-pwm@vger.kernel.org
Cc:     Thierry Reding <thierry.reding@gmail.com>,
        u.kleine-koenig@pengutronix.de, Lee Jones <lee.jones@linaro.org>,
        linux-kernel@vger.kernel.org,
        Clemens Gruber <clemens.gruber@pqgruber.com>
Subject: [PATCH 1/2] pwm: pca9685: fix duty cycle loss on disable/enable
Date:   Thu, 12 Nov 2020 17:37:50 +0100
Message-Id: <20201112163751.204187-1-clemens.gruber@pqgruber.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Currently, disabling a pwm channel clears the OFF registers, which
resets the configured duty cycle. Therefore, after a disable/enable
sequence, the pwm state is not in the same state as it was before.
As a workaround, the user had to do a config call after disable/enable.

Fix it by only toggling the "full-off" bit in disable/enable and no
longer use the "full-on" / "full-off" bits in config.

From now on, the "full-on" bit is only used in GPIO mode and the
"full-off" bit is only used in disable/enable, which also reduces
complexity in the driver.

Signed-off-by: Clemens Gruber <clemens.gruber@pqgruber.com>
---
 drivers/pwm/pwm-pca9685.c | 83 +++++----------------------------------
 1 file changed, 9 insertions(+), 74 deletions(-)

diff --git a/drivers/pwm/pwm-pca9685.c b/drivers/pwm/pwm-pca9685.c
index 4a55dc18656c..df214758256e 100644
--- a/drivers/pwm/pwm-pca9685.c
+++ b/drivers/pwm/pwm-pca9685.c
@@ -283,45 +283,7 @@ static int pca9685_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
 		}
 	}
 
-	if (duty_ns < 1) {
-		if (pwm->hwpwm >= PCA9685_MAXCHAN)
-			reg = PCA9685_ALL_LED_OFF_H;
-		else
-			reg = LED_N_OFF_H(pwm->hwpwm);
-
-		regmap_write(pca->regmap, reg, LED_FULL);
-
-		return 0;
-	}
-
-	if (duty_ns == period_ns) {
-		/* Clear both OFF registers */
-		if (pwm->hwpwm >= PCA9685_MAXCHAN)
-			reg = PCA9685_ALL_LED_OFF_L;
-		else
-			reg = LED_N_OFF_L(pwm->hwpwm);
-
-		regmap_write(pca->regmap, reg, 0x0);
-
-		if (pwm->hwpwm >= PCA9685_MAXCHAN)
-			reg = PCA9685_ALL_LED_OFF_H;
-		else
-			reg = LED_N_OFF_H(pwm->hwpwm);
-
-		regmap_write(pca->regmap, reg, 0x0);
-
-		/* Set the full ON bit */
-		if (pwm->hwpwm >= PCA9685_MAXCHAN)
-			reg = PCA9685_ALL_LED_ON_H;
-		else
-			reg = LED_N_ON_H(pwm->hwpwm);
-
-		regmap_write(pca->regmap, reg, LED_FULL);
-
-		return 0;
-	}
-
-	duty = PCA9685_COUNTER_RANGE * (unsigned long long)duty_ns;
+	duty = (PCA9685_COUNTER_RANGE - 1) * (unsigned long long)duty_ns;
 	duty = DIV_ROUND_UP_ULL(duty, period_ns);
 
 	if (pwm->hwpwm >= PCA9685_MAXCHAN)
@@ -338,14 +300,6 @@ static int pca9685_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
 
 	regmap_write(pca->regmap, reg, ((int)duty >> 8) & 0xf);
 
-	/* Clear the full ON bit, otherwise the set OFF time has no effect */
-	if (pwm->hwpwm >= PCA9685_MAXCHAN)
-		reg = PCA9685_ALL_LED_ON_H;
-	else
-		reg = LED_N_ON_H(pwm->hwpwm);
-
-	regmap_write(pca->regmap, reg, 0);
-
 	return 0;
 }
 
@@ -354,24 +308,6 @@ static int pca9685_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
 	struct pca9685 *pca = to_pca(chip);
 	unsigned int reg;
 
-	/*
-	 * The PWM subsystem does not support a pre-delay.
-	 * So, set the ON-timeout to 0
-	 */
-	if (pwm->hwpwm >= PCA9685_MAXCHAN)
-		reg = PCA9685_ALL_LED_ON_L;
-	else
-		reg = LED_N_ON_L(pwm->hwpwm);
-
-	regmap_write(pca->regmap, reg, 0);
-
-	if (pwm->hwpwm >= PCA9685_MAXCHAN)
-		reg = PCA9685_ALL_LED_ON_H;
-	else
-		reg = LED_N_ON_H(pwm->hwpwm);
-
-	regmap_write(pca->regmap, reg, 0);
-
 	/*
 	 * Clear the full-off bit.
 	 * It has precedence over the others and must be off.
@@ -391,20 +327,16 @@ static void pca9685_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
 	struct pca9685 *pca = to_pca(chip);
 	unsigned int reg;
 
+	/*
+	 * Set the full-off bit.
+	 * It has precedence over the others.
+	 */
 	if (pwm->hwpwm >= PCA9685_MAXCHAN)
 		reg = PCA9685_ALL_LED_OFF_H;
 	else
 		reg = LED_N_OFF_H(pwm->hwpwm);
 
-	regmap_write(pca->regmap, reg, LED_FULL);
-
-	/* Clear the LED_OFF counter. */
-	if (pwm->hwpwm >= PCA9685_MAXCHAN)
-		reg = PCA9685_ALL_LED_OFF_L;
-	else
-		reg = LED_N_OFF_L(pwm->hwpwm);
-
-	regmap_write(pca->regmap, reg, 0x0);
+	regmap_update_bits(pca->regmap, reg, LED_FULL, LED_FULL);
 }
 
 static int pca9685_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
@@ -487,6 +419,9 @@ static int pca9685_pwm_probe(struct i2c_client *client,
 	/* Clear all "full off" bits */
 	regmap_write(pca->regmap, PCA9685_ALL_LED_OFF_L, 0);
 	regmap_write(pca->regmap, PCA9685_ALL_LED_OFF_H, 0);
+	/* Clear all "on" regs */
+	regmap_write(pca->regmap, PCA9685_ALL_LED_ON_L, 0);
+	regmap_write(pca->regmap, PCA9685_ALL_LED_ON_H, 0);
 
 	pca->chip.ops = &pca9685_pwm_ops;
 	/* Add an extra channel for ALL_LED */
-- 
2.29.2