pwm: pca9685: Add error messages for failed regmap calls

Regmap operations can fail if the underlying subsystem is not working
properly (e.g. hogged I2C bus, etc.)
As this is useful information for the user, print an error message if it
happens.
Let probe fail if the first regmap_read or the first regmap_write fails.

Signed-off-by: Clemens Gruber <[e-mail]>
Signed-off-by: Thierry Reding <[e-mail]>

drivers/pwm/pwm-pca9685.c

···
 	return test_bit(channel, pca->pwms_enabled);
 }
 
+static int pca9685_read_reg(struct pca9685 *pca, unsigned int reg, unsigned int *val)
+{
+	struct device *dev = pca->chip.dev;
+	int err;
+
+	err = regmap_read(pca->regmap, reg, val);
+	if (err)
+		dev_err(dev, "regmap_read of register 0x%x failed: %pe\n", reg, ERR_PTR(err));
+
+	return err;
+}
+
+static int pca9685_write_reg(struct pca9685 *pca, unsigned int reg, unsigned int val)
+{
+	struct device *dev = pca->chip.dev;
+	int err;
+
+	err = regmap_write(pca->regmap, reg, val);
+	if (err)
+		dev_err(dev, "regmap_write to register 0x%x failed: %pe\n", reg, ERR_PTR(err));
+
+	return err;
+}
+
 /* Helper function to set the duty cycle ratio to duty/4096 (e.g. duty=2048 -> 50%) */
 static void pca9685_pwm_set_duty(struct pca9685 *pca, int channel, unsigned int duty)
 {
···
 
 	if (duty == 0) {
 		/* Set the full OFF bit, which has the highest precedence */
-		regmap_write(pca->regmap, REG_OFF_H(channel), LED_FULL);
+		pca9685_write_reg(pca, REG_OFF_H(channel), LED_FULL);
 		return;
 	} else if (duty >= PCA9685_COUNTER_RANGE) {
 		/* Set the full ON bit and clear the full OFF bit */
-		regmap_write(pca->regmap, REG_ON_H(channel), LED_FULL);
-		regmap_write(pca->regmap, REG_OFF_H(channel), 0);
+		pca9685_write_reg(pca, REG_ON_H(channel), LED_FULL);
+		pca9685_write_reg(pca, REG_OFF_H(channel), 0);
 		return;
 	}
 
···
 	off = (on + duty) % PCA9685_COUNTER_RANGE;
 
 	/* Set ON time (clears full ON bit) */
-	regmap_write(pca->regmap, REG_ON_L(channel), on & 0xff);
-	regmap_write(pca->regmap, REG_ON_H(channel), (on >> 8) & 0xf);
+	pca9685_write_reg(pca, REG_ON_L(channel), on & 0xff);
+	pca9685_write_reg(pca, REG_ON_H(channel), (on >> 8) & 0xf);
 	/* Set OFF time (clears full OFF bit) */
-	regmap_write(pca->regmap, REG_OFF_L(channel), off & 0xff);
-	regmap_write(pca->regmap, REG_OFF_H(channel), (off >> 8) & 0xf);
+	pca9685_write_reg(pca, REG_OFF_L(channel), off & 0xff);
+	pca9685_write_reg(pca, REG_OFF_H(channel), (off >> 8) & 0xf);
 }
 
 static unsigned int pca9685_pwm_get_duty(struct pca9685 *pca, int channel)
···
 		return 0;
 	}
 
-	regmap_read(pca->regmap, LED_N_OFF_H(channel), &off);
+	pca9685_read_reg(pca, LED_N_OFF_H(channel), &off);
 	if (off & LED_FULL) {
 		/* Full OFF bit is set */
 		return 0;
 	}
 
-	regmap_read(pca->regmap, LED_N_ON_H(channel), &on);
+	pca9685_read_reg(pca, LED_N_ON_H(channel), &on);
 	if (on & LED_FULL) {
 		/* Full ON bit is set */
 		return PCA9685_COUNTER_RANGE;
 	}
 
-	regmap_read(pca->regmap, LED_N_OFF_L(channel), &val);
+	pca9685_read_reg(pca, LED_N_OFF_L(channel), &val);
 	off = ((off & 0xf) << 8) | (val & 0xff);
 	if (!pwm->state.usage_power)
 		return off;
 
 	/* Read ON register to calculate duty cycle of staggered output */
-	if (regmap_read(pca->regmap, LED_N_ON_L(channel), &val)) {
+	if (pca9685_read_reg(pca, LED_N_ON_L(channel), &val)) {
 		/* Reset val to 0 in case reading LED_N_ON_L failed */
 		val = 0;
 	}
···
 
 static void pca9685_set_sleep_mode(struct pca9685 *pca, bool enable)
 {
-	regmap_update_bits(pca->regmap, PCA9685_MODE1,
-			   MODE1_SLEEP, enable ? MODE1_SLEEP : 0);
+	struct device *dev = pca->chip.dev;
+	int err = regmap_update_bits(pca->regmap, PCA9685_MODE1,
+				     MODE1_SLEEP, enable ? MODE1_SLEEP : 0);
+	if (err) {
+		dev_err(dev, "regmap_update_bits of register 0x%x failed: %pe\n",
+			PCA9685_MODE1, ERR_PTR(err));
+		return;
+	}
+
 	if (!enable) {
 		/* Wait 500us for the oscillator to be back up */
 		udelay(500);
···
 		return 0;
 	}
 
-	regmap_read(pca->regmap, PCA9685_PRESCALE, &val);
+	pca9685_read_reg(pca, PCA9685_PRESCALE, &val);
 	if (prescale != val) {
 		if (!pca9685_prescaler_can_change(pca, pwm->hwpwm)) {
 			dev_err(chip->dev,
···
 		pca9685_set_sleep_mode(pca, true);
 
 		/* Change the chip-wide output frequency */
-		regmap_write(pca->regmap, PCA9685_PRESCALE, prescale);
+		pca9685_write_reg(pca, PCA9685_PRESCALE, prescale);
 
 		/* Wake the chip up */
 		pca9685_set_sleep_mode(pca, false);
···
 	unsigned int val = 0;
 
 	/* Calculate (chip-wide) period from prescale value */
-	regmap_read(pca->regmap, PCA9685_PRESCALE, &val);
+	pca9685_read_reg(pca, PCA9685_PRESCALE, &val);
 	/*
 	 * PCA9685_OSC_CLOCK_MHZ is 25, i.e. an integer divider of 1000.
 	 * The following calculation is therefore only a multiplication
···
 
 	mutex_init(&pca->lock);
 
-	regmap_read(pca->regmap, PCA9685_MODE2, &reg);
+	ret = pca9685_read_reg(pca, PCA9685_MODE2, &reg);
+	if (ret)
+		return ret;
 
 	if (device_property_read_bool(&client->dev, "invert"))
 		reg |= MODE2_INVRT;
···
 	else
 		reg |= MODE2_OUTDRV;
 
-	regmap_write(pca->regmap, PCA9685_MODE2, reg);
+	ret = pca9685_write_reg(pca, PCA9685_MODE2, reg);
+	if (ret)
+		return ret;
 
 	/* Disable all LED ALLCALL and SUBx addresses to avoid bus collisions */
-	regmap_read(pca->regmap, PCA9685_MODE1, &reg);
+	pca9685_read_reg(pca, PCA9685_MODE1, &reg);
 	reg &= ~(MODE1_ALLCALL | MODE1_SUB1 | MODE1_SUB2 | MODE1_SUB3);
-	regmap_write(pca->regmap, PCA9685_MODE1, reg);
+	pca9685_write_reg(pca, PCA9685_MODE1, reg);
 
 	/* Reset OFF/ON registers to POR default */
-	regmap_write(pca->regmap, PCA9685_ALL_LED_OFF_L, LED_FULL);
-	regmap_write(pca->regmap, PCA9685_ALL_LED_OFF_H, LED_FULL);
-	regmap_write(pca->regmap, PCA9685_ALL_LED_ON_L, 0);
-	regmap_write(pca->regmap, PCA9685_ALL_LED_ON_H, 0);
+	pca9685_write_reg(pca, PCA9685_ALL_LED_OFF_L, LED_FULL);
+	pca9685_write_reg(pca, PCA9685_ALL_LED_OFF_H, LED_FULL);
+	pca9685_write_reg(pca, PCA9685_ALL_LED_ON_L, 0);
+	pca9685_write_reg(pca, PCA9685_ALL_LED_ON_H, 0);
 
 	pca->chip.ops = &pca9685_pwm_ops;
 	/* Add an extra channel for ALL_LED */