iio: humidity: hts221: add vdd voltage regulator

Like all other ST sensors, hts221 devices have VDD power line.
Introduce VDD voltage regulator to control it.
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://lore.kernel.org/r/6b3347e78f4f920c48eb6a66936d3b69cb9ff53a.1606045688.git.lorenzo@kernel.orgSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/humidity/hts221.h

@@ -13,6 +13,7 @@
 #define HTS221_DEV_NAME		"hts221"
 
 #include <linux/iio/iio.h>
+#include <linux/regulator/consumer.h>
 
 enum hts221_sensor_type {
 	HTS221_SENSOR_H,
@@ -29,6 +30,7 @@ struct hts221_hw {
 	const char *name;
 	struct device *dev;
 	struct regmap *regmap;
+	struct regulator *vdd;
 
 	struct iio_trigger *trig;
 	int irq;

drivers/iio/humidity/hts221_core.c

@@ -547,6 +547,35 @@ static const struct iio_info hts221_info = {
 
 static const unsigned long hts221_scan_masks[] = {0x3, 0x0};
 
+static int hts221_init_regulators(struct device *dev)
+{
+	struct iio_dev *iio_dev = dev_get_drvdata(dev);
+	struct hts221_hw *hw = iio_priv(iio_dev);
+	int err;
+
+	hw->vdd = devm_regulator_get(dev, "vdd");
+	if (IS_ERR(hw->vdd))
+		return dev_err_probe(dev, PTR_ERR(hw->vdd),
+				     "failed to get vdd regulator\n");
+
+	err = regulator_enable(hw->vdd);
+	if (err) {
+		dev_err(dev, "failed to enable vdd regulator: %d\n", err);
+		return err;
+	}
+
+	msleep(50);
+
+	return 0;
+}
+
+static void hts221_chip_uninit(void *data)
+{
+	struct hts221_hw *hw = data;
+
+	regulator_disable(hw->vdd);
+}
+
 int hts221_probe(struct device *dev, int irq, const char *name,
 		 struct regmap *regmap)
 {
@@ -567,6 +596,14 @@ int hts221_probe(struct device *dev, int irq, const char *name,
 	hw->irq = irq;
 	hw->regmap = regmap;
 
+	err = hts221_init_regulators(dev);
+	if (err)
+		return err;
+
+	err = devm_add_action_or_reset(dev, hts221_chip_uninit, hw);
+	if (err)
+		return err;
+
 	err = hts221_check_whoami(hw);
 	if (err < 0)
 		return err;