regulator: max8973: add mechanism to enable/disable through GPIO

MAX8973 supports the voltage output enable/disable through its EN
pin. This EN pin can be connected through GPIO from host processor.
Add support to provide GPIO number from platform/DT and if it is
valid GPIO then enable external control default.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/regulator/max8973-regulator.txt

@@ -12,6 +12,8 @@ Optional properties:
 
 -maxim,externally-enable: boolean, externally control the regulator output
 		enable/disable.
+-maxim,enable-gpio: GPIO for enable control. If the valid GPIO is provided
+		then externally enable control will be considered.
 -maxim,dvs-gpio: GPIO which is connected to DVS pin of device.
 -maxim,dvs-default-state: Default state of GPIO during initialisation.
 		1 for HIGH and 0 for LOW.

drivers/regulator/max8973-regulator.c

@@ -96,6 +96,7 @@ struct max8973_chip {
 	struct regulator_desc desc;
 	struct regmap *regmap;
 	bool enable_external_control;
+	int enable_gpio;
 	int dvs_gpio;
 	int lru_index[MAX8973_MAX_VOUT_REG];
 	int curr_vout_val[MAX8973_MAX_VOUT_REG];
@@ -379,6 +380,7 @@ static struct max8973_regulator_platform_data *max8973_parse_dt(
 
 	pdata->enable_ext_control = of_property_read_bool(np,
 						"maxim,externally-enable");
+	pdata->enable_gpio = of_get_named_gpio(np, "maxim,enable-gpio", 0);
 	pdata->dvs_gpio = of_get_named_gpio(np, "maxim,dvs-gpio", 0);
 
 	ret = of_property_read_u32(np, "maxim,dvs-default-state", &pval);
@@ -409,6 +411,7 @@ static int max8973_probe(struct i2c_client *client,
 			 const struct i2c_device_id *id)
 {
 	struct max8973_regulator_platform_data *pdata;
+	struct regulator_init_data *ridata;
 	struct regulator_config config = { };
 	struct regulator_dev *rdev;
 	struct max8973_chip *max;
@@ -427,7 +430,8 @@ static int max8973_probe(struct i2c_client *client,
 		return -EIO;
 	}
 
-	if (pdata->dvs_gpio == -EPROBE_DEFER)
+	if ((pdata->dvs_gpio == -EPROBE_DEFER) ||
+		(pdata->enable_gpio == -EPROBE_DEFER))
 		return -EPROBE_DEFER;
 
 	max = devm_kzalloc(&client->dev, sizeof(*max), GFP_KERNEL);
@@ -453,6 +457,15 @@ static int max8973_probe(struct i2c_client *client,
 	max->desc.uV_step = MAX8973_VOLATGE_STEP;
 	max->desc.n_voltages = MAX8973_BUCK_N_VOLTAGE;
 
+	max->dvs_gpio = (pdata->dvs_gpio) ? pdata->dvs_gpio : -EINVAL;
+	max->enable_gpio = (pdata->enable_gpio) ? pdata->enable_gpio : -EINVAL;
+	max->enable_external_control = pdata->enable_ext_control;
+	max->curr_gpio_val = pdata->dvs_def_state;
+	max->curr_vout_reg = MAX8973_VOUT + pdata->dvs_def_state;
+
+	if (gpio_is_valid(max->enable_gpio))
+		max->enable_external_control = true;
+
 	if (!pdata->enable_ext_control) {
 		max->desc.enable_reg = MAX8973_VOUT;
 		max->desc.enable_mask = MAX8973_VOUT_ENABLE;
@@ -461,11 +474,6 @@ static int max8973_probe(struct i2c_client *client,
 		max->ops.is_enabled = regulator_is_enabled_regmap;
 	}
 
-	max->dvs_gpio = (pdata->dvs_gpio) ? pdata->dvs_gpio : -EINVAL;
-	max->enable_external_control = pdata->enable_ext_control;
-	max->curr_gpio_val = pdata->dvs_def_state;
-	max->curr_vout_reg = MAX8973_VOUT + pdata->dvs_def_state;
-
 	max->lru_index[0] = max->curr_vout_reg;
 
 	if (gpio_is_valid(max->dvs_gpio)) {
@@ -509,6 +517,15 @@ static int max8973_probe(struct i2c_client *client,
 	config.of_node = client->dev.of_node;
 	config.regmap = max->regmap;
 
+	if (gpio_is_valid(max->enable_gpio)) {
+		ridata = pdata->reg_init_data;
+		config.ena_gpio_flags = GPIOF_OUT_INIT_LOW;
+		if (ridata && (ridata->constraints.always_on ||
+			ridata->constraints.boot_on))
+			config.ena_gpio_flags = GPIOF_OUT_INIT_HIGH;
+		config.ena_gpio = max->enable_gpio;
+	}
+
 	/* Register the regulators */
 	rdev = devm_regulator_register(&client->dev, &max->desc, &config);
 	if (IS_ERR(rdev)) {

include/linux/regulator/max8973-regulator.h

@@ -58,6 +58,9 @@
  *		control signal from EN input pin. If it is false then
  *		voltage output will be enabled/disabled through EN bit of
  *		device register.
+ * @enable_gpio: Enable GPIO. If EN pin is controlled through GPIO from host
+ *		then GPIO number can be provided. If no GPIO controlled then
+ *		it should be -1.
  * @dvs_gpio: GPIO for dvs. It should be -1 if this is tied with fixed logic.
  * @dvs_def_state: Default state of dvs. 1 if it is high else 0.
  */
@@ -65,6 +68,7 @@ struct max8973_regulator_platform_data {
 	struct regulator_init_data *reg_init_data;
 	unsigned long control_flags;
 	bool enable_ext_control;
+	int enable_gpio;
 	int dvs_gpio;
 	unsigned dvs_def_state:1;
 };