pwm-pca9685: Fix several driver bugs

Problems:
- When duty_ns == period_ns, the full OFF bit was not cleared and the
  PWM output of the PCA9685 stayed off.
- When duty_ns == period_ns and the catch-all channel was used, the
  ALL_LED_OFF_L register was not cleared.
- The full ON bit was not cleared when setting the OFF time, therefore
  the exact OFF time was ignored when setting a duty_ns < period_ns

Solution: Clear both OFF registers when setting full ON and clear the
full ON bit when changing the OFF registers.

Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Signed-off-by: Clemens Gruber <clemens.gruber@pqgruber.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

diff --git a/drivers/pwm/pwm-pca9685.c b/drivers/pwm/pwm-pca9685.c
index bd5f0276db049a36b8f67aac959b347c5c284b70..0d17d99b749b6cfe43f7b3e3e8f17be3acd38f7a 100644 (file)
--- a/drivers/pwm/pwm-pca9685.c
+++ b/drivers/pwm/pwm-pca9685.c
@@ -85,6 +85,22 @@ static int pca9685_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
        }
 
        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
@@ -112,6 +128,14 @@ 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;
 }