iio: mma8452: add support for runtime power management

This adds support for runtime power management and, if configured, activates
automatic standby after 2 seconds of inactivity.

Inactivity means no read of acceleration values and no events triggered or
activated.

If CONFIG_PM is not set, this doesn't change anything for existing users.
Signed-off-by: Martin Kepplinger <martink@posteo.de>
Signed-off-by: Christoph Muellner <christoph.muellner@theobroma-systems.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/accel/mma8452.c

@@ -31,6 +31,7 @@
 #include <linux/delay.h>
 #include <linux/of_device.h>
 #include <linux/of_irq.h>
+#include <linux/pm_runtime.h>
 
 #define MMA8452_STATUS				0x00
 #define  MMA8452_STATUS_DRDY			(BIT(2) | BIT(1) | BIT(0))
@@ -92,6 +93,8 @@
 #define MMA8652_DEVICE_ID			0x4a
 #define MMA8653_DEVICE_ID			0x5a
 
+#define MMA8452_AUTO_SUSPEND_DELAY_MS		2000
+
 struct mma8452_data {
 	struct i2c_client *client;
 	struct mutex lock;
@@ -172,6 +175,31 @@ static int mma8452_drdy(struct mma8452_data *data)
 	return -EIO;
 }
 
+static int mma8452_set_runtime_pm_state(struct i2c_client *client, bool on)
+{
+#ifdef CONFIG_PM
+	int ret;
+
+	if (on) {
+		ret = pm_runtime_get_sync(&client->dev);
+	} else {
+		pm_runtime_mark_last_busy(&client->dev);
+		ret = pm_runtime_put_autosuspend(&client->dev);
+	}
+
+	if (ret < 0) {
+		dev_err(&client->dev,
+			"failed to change power state to %d\n", on);
+		if (on)
+			pm_runtime_put_noidle(&client->dev);
+
+		return ret;
+	}
+#endif
+
+	return 0;
+}
+
 static int mma8452_read(struct mma8452_data *data, __be16 buf[3])
 {
 	int ret = mma8452_drdy(data);
@@ -179,8 +207,16 @@ static int mma8452_read(struct mma8452_data *data, __be16 buf[3])
 	if (ret < 0)
 		return ret;
 
-	return i2c_smbus_read_i2c_block_data(data->client, MMA8452_OUT_X,
-					     3 * sizeof(__be16), (u8 *)buf);
+	ret = mma8452_set_runtime_pm_state(data->client, true);
+	if (ret)
+		return ret;
+
+	ret = i2c_smbus_read_i2c_block_data(data->client, MMA8452_OUT_X,
+					    3 * sizeof(__be16), (u8 *)buf);
+
+	ret = mma8452_set_runtime_pm_state(data->client, false);
+
+	return ret;
 }
 
 static ssize_t mma8452_show_int_plus_micros(char *buf, const int (*vals)[2],
@@ -707,7 +743,11 @@ static int mma8452_write_event_config(struct iio_dev *indio_dev,
 {
 	struct mma8452_data *data = iio_priv(indio_dev);
 	const struct mma_chip_info *chip = data->chip_info;
-	int val;
+	int val, ret;
+
+	ret = mma8452_set_runtime_pm_state(data->client, state);
+	if (ret)
+		return ret;
 
 	switch (dir) {
 	case IIO_EV_DIR_FALLING:
@@ -1139,7 +1179,11 @@ static int mma8452_data_rdy_trigger_set_state(struct iio_trigger *trig,
 {
 	struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
 	struct mma8452_data *data = iio_priv(indio_dev);
-	int reg;
+	int reg, ret;
+
+	ret = mma8452_set_runtime_pm_state(data->client, state);
+	if (ret)
+		return ret;
 
 	reg = i2c_smbus_read_byte_data(data->client, MMA8452_CTRL_REG4);
 	if (reg < 0)
@@ -1365,6 +1409,15 @@ static int mma8452_probe(struct i2c_client *client,
 			goto buffer_cleanup;
 	}
 
+	ret = pm_runtime_set_active(&client->dev);
+	if (ret < 0)
+		goto buffer_cleanup;
+
+	pm_runtime_enable(&client->dev);
+	pm_runtime_set_autosuspend_delay(&client->dev,
+					 MMA8452_AUTO_SUSPEND_DELAY_MS);
+	pm_runtime_use_autosuspend(&client->dev);
+
 	ret = iio_device_register(indio_dev);
 	if (ret < 0)
 		goto buffer_cleanup;
@@ -1389,6 +1442,11 @@ static int mma8452_remove(struct i2c_client *client)
 	struct iio_dev *indio_dev = i2c_get_clientdata(client);
 
 	iio_device_unregister(indio_dev);
+
+	pm_runtime_disable(&client->dev);
+	pm_runtime_set_suspended(&client->dev);
+	pm_runtime_put_noidle(&client->dev);
+
 	iio_triggered_buffer_cleanup(indio_dev);
 	mma8452_trigger_cleanup(indio_dev);
 	mma8452_standby(iio_priv(indio_dev));
@@ -1396,6 +1454,45 @@ static int mma8452_remove(struct i2c_client *client)
 	return 0;
 }
 
+#ifdef CONFIG_PM
+static int mma8452_runtime_suspend(struct device *dev)
+{
+	struct iio_dev *indio_dev = i2c_get_clientdata(to_i2c_client(dev));
+	struct mma8452_data *data = iio_priv(indio_dev);
+	int ret;
+
+	mutex_lock(&data->lock);
+	ret = mma8452_standby(data);
+	mutex_unlock(&data->lock);
+	if (ret < 0) {
+		dev_err(&data->client->dev, "powering off device failed\n");
+		return -EAGAIN;
+	}
+
+	return 0;
+}
+
+static int mma8452_runtime_resume(struct device *dev)
+{
+	struct iio_dev *indio_dev = i2c_get_clientdata(to_i2c_client(dev));
+	struct mma8452_data *data = iio_priv(indio_dev);
+	int ret, sleep_val;
+
+	ret = mma8452_active(data);
+	if (ret < 0)
+		return ret;
+
+	ret = mma8452_get_odr_index(data);
+	sleep_val = 1000 / mma8452_samp_freq[ret][0];
+	if (sleep_val < 20)
+		usleep_range(sleep_val * 1000, 20000);
+	else
+		msleep_interruptible(sleep_val);
+
+	return 0;
+}
+#endif
+
 #ifdef CONFIG_PM_SLEEP
 static int mma8452_suspend(struct device *dev)
 {
@@ -1408,13 +1505,14 @@ static int mma8452_resume(struct device *dev)
 	return mma8452_active(iio_priv(i2c_get_clientdata(
 		to_i2c_client(dev))));
 }
-
-static SIMPLE_DEV_PM_OPS(mma8452_pm_ops, mma8452_suspend, mma8452_resume);
-#define MMA8452_PM_OPS (&mma8452_pm_ops)
-#else
-#define MMA8452_PM_OPS NULL
 #endif
 
+static const struct dev_pm_ops mma8452_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(mma8452_suspend, mma8452_resume)
+	SET_RUNTIME_PM_OPS(mma8452_runtime_suspend,
+			   mma8452_runtime_resume, NULL)
+};
+
 static const struct i2c_device_id mma8452_id[] = {
 	{ "mma8452", mma8452 },
 	{ "mma8453", mma8453 },
@@ -1428,7 +1526,7 @@ static struct i2c_driver mma8452_driver = {
 	.driver = {
 		.name	= "mma8452",
 		.of_match_table = of_match_ptr(mma8452_dt_ids),
-		.pm	= MMA8452_PM_OPS,
+		.pm	= &mma8452_pm_ops,
 	},
 	.probe = mma8452_probe,
 	.remove = mma8452_remove,