iio: humidity: hdc3020: add power management

The HDC3020 sensor carries out periodic measurements during normal
operation, but as long as the power supply is enabled, it will carry on
in low-power modes. In order to avoid that and reduce power consumption,
the device can be switched to Trigger-on Demand mode, and if possible,
turn off its regulator.

According to the datasheet, the maximum "Power Up Ready" is 5 ms.

Add resume/suspend pm operations to manage measurement mode and
regulator state.
Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Link: https://lore.kernel.org/r/20240303-hdc3020-pm-v3-1-48bc02b5241b@gmail.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/humidity/hdc3020.c

@@ -20,6 +20,8 @@
 #include <linux/interrupt.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
+#include <linux/pm.h>
+#include <linux/regulator/consumer.h>
 #include <linux/units.h>
 
 #include <asm/unaligned.h>
@@ -68,6 +70,7 @@
 
 struct hdc3020_data {
 	struct i2c_client *client;
+	struct regulator *vdd_supply;
 	/*
 	 * Ensure that the sensor configuration (currently only heater is
 	 * supported) will not be changed during the process of reading
@@ -551,9 +554,45 @@ static const struct iio_info hdc3020_info = {
 	.write_event_value = hdc3020_write_thresh,
 };
 
-static void hdc3020_stop(void *data)
+static int hdc3020_power_off(struct hdc3020_data *data)
 {
-	hdc3020_exec_cmd((struct hdc3020_data *)data, HDC3020_EXIT_AUTO);
+	hdc3020_exec_cmd(data, HDC3020_EXIT_AUTO);
+
+	return regulator_disable(data->vdd_supply);
+}
+
+static int hdc3020_power_on(struct hdc3020_data *data)
+{
+	int ret;
+
+	ret = regulator_enable(data->vdd_supply);
+	if (ret)
+		return ret;
+
+	fsleep(5000);
+
+	if (data->client->irq) {
+		/*
+		 * The alert output is activated by default upon power up,
+		 * hardware reset, and soft reset. Clear the status register.
+		 */
+		ret = hdc3020_exec_cmd(data, HDC3020_S_STATUS);
+		if (ret) {
+			hdc3020_power_off(data);
+			return ret;
+		}
+	}
+
+	ret = hdc3020_exec_cmd(data, HDC3020_S_AUTO_10HZ_MOD0);
+	if (ret)
+		hdc3020_power_off(data);
+
+	return ret;
+}
+
+static void hdc3020_exit(void *data)
+{
+	hdc3020_power_off(data);
 }
 
 static int hdc3020_probe(struct i2c_client *client)
@@ -569,6 +608,8 @@ static int hdc3020_probe(struct i2c_client *client)
 	if (!indio_dev)
 		return -ENOMEM;
 
+	dev_set_drvdata(&client->dev, indio_dev);
+
 	data = iio_priv(indio_dev);
 	data->client = client;
 	mutex_init(&data->lock);
@@ -580,6 +621,20 @@ static int hdc3020_probe(struct i2c_client *client)
 	indio_dev->info = &hdc3020_info;
 	indio_dev->channels = hdc3020_channels;
 	indio_dev->num_channels = ARRAY_SIZE(hdc3020_channels);
+
+	data->vdd_supply = devm_regulator_get(&client->dev, "vdd");
+	if (IS_ERR(data->vdd_supply))
+		return dev_err_probe(&client->dev, PTR_ERR(data->vdd_supply),
+				     "Unable to get VDD regulator\n");
+
+	ret = hdc3020_power_on(data);
+	if (ret)
+		return dev_err_probe(&client->dev, ret, "Power on failed\n");
+
+	ret = devm_add_action_or_reset(&data->client->dev, hdc3020_exit, data);
+	if (ret)
+		return ret;
+
 	if (client->irq) {
 		ret = devm_request_threaded_irq(&client->dev, client->irq,
 						NULL, hdc3020_interrupt_handler,
@@ -588,25 +643,8 @@ static int hdc3020_probe(struct i2c_client *client)
 		if (ret)
 			return dev_err_probe(&client->dev, ret,
 					     "Failed to request IRQ\n");
-
-		/*
-		 * The alert output is activated by default upon power up,
-		 * hardware reset, and soft reset. Clear the status register.
-		 */
-		ret = hdc3020_exec_cmd(data, HDC3020_S_STATUS);
-		if (ret)
-			return ret;
 	}
 
-	ret = hdc3020_exec_cmd(data, HDC3020_S_AUTO_10HZ_MOD0);
-	if (ret)
-		return dev_err_probe(&client->dev, ret,
-				     "Unable to set up measurement\n");
-
-	ret = devm_add_action_or_reset(&data->client->dev, hdc3020_stop, data);
-	if (ret)
-		return ret;
-
 	ret = devm_iio_device_register(&data->client->dev, indio_dev);
 	if (ret)
 		return dev_err_probe(&client->dev, ret, "Failed to add device");
@@ -614,6 +652,24 @@ static int hdc3020_probe(struct i2c_client *client)
 	return 0;
 }
 
+static int hdc3020_suspend(struct device *dev)
+{
+	struct iio_dev *iio_dev = dev_get_drvdata(dev);
+	struct hdc3020_data *data = iio_priv(iio_dev);
+
+	return hdc3020_power_off(data);
+}
+
+static int hdc3020_resume(struct device *dev)
+{
+	struct iio_dev *iio_dev = dev_get_drvdata(dev);
+	struct hdc3020_data *data = iio_priv(iio_dev);
+
+	return hdc3020_power_on(data);
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(hdc3020_pm_ops, hdc3020_suspend, hdc3020_resume);
+
 static const struct i2c_device_id hdc3020_id[] = {
 	{ "hdc3020" },
 	{ "hdc3021" },
@@ -633,6 +689,7 @@ MODULE_DEVICE_TABLE(of, hdc3020_dt_ids);
 static struct i2c_driver hdc3020_driver = {
 	.driver = {
 		.name = "hdc3020",
+		.pm = pm_sleep_ptr(&hdc3020_pm_ops),
 		.of_match_table = hdc3020_dt_ids,
 	},
 	.probe = hdc3020_probe,