leds: lm3692x: Disable chip on brightness 0

Otherwise there's a noticeable glow even with brightness 0. Also
turning off the regulator can save additional power.
Signed-off-by: Guido Günther <agx@sigxcpu.org>
Signed-off-by: Pavel Machek <pavel@ucw.cz>

drivers/leds/leds-lm3692x.c

@@ -116,7 +116,8 @@ struct lm3692x_led {
 	int led_enable;
 	int model_id;
 
-	u8 boost_ctrl;
+	u8 boost_ctrl, brightness_ctrl;
+	bool enabled;
 };
 
 static const struct reg_default lm3692x_reg_defs[] = {
@@ -170,6 +171,9 @@ static int lm3692x_leds_enable(struct lm3692x_led *led)
 	int enable_state;
 	int ret, reg_ret;
 
+	if (led->enabled)
+		return 0;
+
 	if (led->regulator) {
 		ret = regulator_enable(led->regulator);
 		if (ret) {
@@ -272,6 +276,7 @@ static int lm3692x_leds_enable(struct lm3692x_led *led)
 	ret = regmap_update_bits(led->regmap, LM3692X_EN, LM3692X_ENABLE_MASK,
 				 enable_state | LM3692X_DEVICE_EN);
 
+	led->enabled = true;
 	return ret;
 out:
 	dev_err(&led->client->dev, "Fail writing initialization values\n");
@@ -293,6 +298,9 @@ static int lm3692x_leds_disable(struct lm3692x_led *led)
 {
 	int ret;
 
+	if (!led->enabled)
+		return 0;
+
 	ret = regmap_update_bits(led->regmap, LM3692X_EN, LM3692X_DEVICE_EN, 0);
 	if (ret) {
 		dev_err(&led->client->dev, "Failed to disable regulator: %d\n",
@@ -310,6 +318,7 @@ static int lm3692x_leds_disable(struct lm3692x_led *led)
 				"Failed to disable regulator: %d\n", ret);
 	}
 
+	led->enabled = false;
 	return ret;
 }
 
@@ -323,6 +332,13 @@ static int lm3692x_brightness_set(struct led_classdev *led_cdev,
 
 	mutex_lock(&led->lock);
 
+	if (brt_val == 0) {
+		ret = lm3692x_leds_disable(led);
+		goto out;
+	} else {
+		lm3692x_leds_enable(led);
+	}
+
 	ret = lm3692x_fault_check(led);
 	if (ret) {
 		dev_err(&led->client->dev, "Cannot read/clear faults: %d\n",