staging: iio: isl29028: add runtime power management support

This patch adds runtime power management support to the isl29028 driver.
It defaults to powering off the device after two seconds of inactivity.

isl29028_chip_init_and_power_on() currently only zeros the CONFIGURE
register on the chip, which will cause the chip to turn off. This patch
also renames that function to isl29028_clear_configure_reg() since it is
now used in several places.

Signed-off-by: Brian Masney <masneyb@onstation.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/staging/iio/light/isl29028.c

@@ -26,6 +26,7 @@
 #include <linux/regmap.h>
 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>
+#include <linux/pm_runtime.h>
 
 #define ISL29028_CONV_TIME_MS			100
 
@@ -60,6 +61,8 @@
 
 #define ISL29028_NUM_REGS			(ISL29028_REG_TEST2_MODE + 1)
 
+#define ISL29028_POWER_OFF_DELAY_MS		2000
+
 enum isl29028_als_ir_mode {
 	ISL29028_MODE_NONE = 0,
 	ISL29028_MODE_ALS,
@@ -297,16 +300,39 @@ static int isl29028_ir_get(struct isl29028_chip *chip, int *ir_data)
 	return isl29028_read_als_ir(chip, ir_data);
 }
 
+static int isl29028_set_pm_runtime_busy(struct isl29028_chip *chip, bool on)
+{
+	struct device *dev = regmap_get_device(chip->regmap);
+	int ret;
+
+	if (on) {
+		ret = pm_runtime_get_sync(dev);
+		if (ret < 0)
+			pm_runtime_put_noidle(dev);
+	} else {
+		pm_runtime_mark_last_busy(dev);
+		ret = pm_runtime_put_autosuspend(dev);
+	}
+
+	return ret;
+}
+
 /* Channel IO */
 static int isl29028_write_raw(struct iio_dev *indio_dev,
 			      struct iio_chan_spec const *chan,
 			      int val, int val2, long mask)
 {
 	struct isl29028_chip *chip = iio_priv(indio_dev);
 	struct device *dev = regmap_get_device(chip->regmap);
-	int ret = -EINVAL;
+	int ret;
+
+	ret = isl29028_set_pm_runtime_busy(chip, true);
+	if (ret < 0)
+		return ret;
 
 	mutex_lock(&chip->lock);
+
+	ret = -EINVAL;
 	switch (chan->type) {
 	case IIO_PROXIMITY:
 		if (mask != IIO_CHAN_INFO_SAMP_FREQ) {
@@ -350,6 +376,13 @@ static int isl29028_write_raw(struct iio_dev *indio_dev,
 
 	mutex_unlock(&chip->lock);
 
+	if (ret < 0)
+		return ret;
+
+	ret = isl29028_set_pm_runtime_busy(chip, false);
+	if (ret < 0)
+		return ret;
+
 	return ret;
 }
 
@@ -359,9 +392,15 @@ static int isl29028_read_raw(struct iio_dev *indio_dev,
 {
 	struct isl29028_chip *chip = iio_priv(indio_dev);
 	struct device *dev = regmap_get_device(chip->regmap);
-	int ret = -EINVAL;
+	int ret, pm_ret;
+
+	ret = isl29028_set_pm_runtime_busy(chip, true);
+	if (ret < 0)
+		return ret;
 
 	mutex_lock(&chip->lock);
+
+	ret = -EINVAL;
 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
 	case IIO_CHAN_INFO_PROCESSED:
@@ -405,6 +444,18 @@ static int isl29028_read_raw(struct iio_dev *indio_dev,
 
 	mutex_unlock(&chip->lock);
 
+	if (ret < 0)
+		return ret;
+
+	/**
+	 * Preserve the ret variable if the call to
+	 * isl29028_set_pm_runtime_busy() is successful so the reading
+	 * (if applicable) is returned to user space.
+	 */
+	pm_ret = isl29028_set_pm_runtime_busy(chip, false);
+	if (pm_ret < 0)
+		return pm_ret;
+
 	return ret;
 }
 
@@ -445,17 +496,18 @@ static const struct iio_info isl29028_info = {
 	.write_raw = isl29028_write_raw,
 };
 
-static int isl29028_chip_init_and_power_on(struct isl29028_chip *chip)
+static int isl29028_clear_configure_reg(struct isl29028_chip *chip)
 {
 	struct device *dev = regmap_get_device(chip->regmap);
 	int ret;
 
 	ret = regmap_write(chip->regmap, ISL29028_REG_CONFIGURE, 0x0);
-	if (ret < 0) {
+	if (ret < 0)
 		dev_err(dev, "%s(): Error %d clearing the CONFIGURE register\n",
 			__func__, ret);
-		return ret;
-	}
+
+	chip->als_ir_mode = ISL29028_MODE_NONE;
+	chip->enable_prox = false;
 
 	return ret;
 }
@@ -509,7 +561,6 @@ static int isl29028_probe(struct i2c_client *client,
 	chip->enable_prox  = false;
 	chip->prox_sampling = 20;
 	chip->lux_scale = 2000;
-	chip->als_ir_mode = ISL29028_MODE_NONE;
 
 	ret = regmap_write(chip->regmap, ISL29028_REG_TEST1_MODE, 0x0);
 	if (ret < 0) {
@@ -527,7 +578,7 @@ static int isl29028_probe(struct i2c_client *client,
 		return ret;
 	}
 
-	ret = isl29028_chip_init_and_power_on(chip);
+	ret = isl29028_clear_configure_reg(chip);
 	if (ret < 0)
 		return ret;
 
@@ -538,6 +589,11 @@ static int isl29028_probe(struct i2c_client *client,
 	indio_dev->dev.parent = &client->dev;
 	indio_dev->modes = INDIO_DIRECT_MODE;
 
+	pm_runtime_enable(&client->dev);
+	pm_runtime_set_autosuspend_delay(&client->dev,
+					 ISL29028_POWER_OFF_DELAY_MS);
+	pm_runtime_use_autosuspend(&client->dev);
+
 	ret = devm_iio_device_register(indio_dev->dev.parent, indio_dev);
 	if (ret < 0) {
 		dev_err(&client->dev,
@@ -549,6 +605,50 @@ static int isl29028_probe(struct i2c_client *client,
 	return 0;
 }
 
+static int isl29028_remove(struct i2c_client *client)
+{
+	struct iio_dev *indio_dev = i2c_get_clientdata(client);
+	struct isl29028_chip *chip = iio_priv(indio_dev);
+
+	iio_device_unregister(indio_dev);
+
+	pm_runtime_disable(&client->dev);
+	pm_runtime_set_suspended(&client->dev);
+	pm_runtime_put_noidle(&client->dev);
+
+	return isl29028_clear_configure_reg(chip);
+}
+
+static int __maybe_unused isl29028_suspend(struct device *dev)
+{
+	struct iio_dev *indio_dev = i2c_get_clientdata(to_i2c_client(dev));
+	struct isl29028_chip *chip = iio_priv(indio_dev);
+	int ret;
+
+	mutex_lock(&chip->lock);
+
+	ret = isl29028_clear_configure_reg(chip);
+
+	mutex_unlock(&chip->lock);
+
+	return ret;
+}
+
+static int __maybe_unused isl29028_resume(struct device *dev)
+{
+	/**
+	 * The specific component (ALS/IR or proximity) will enable itself as
+	 * needed the next time that the user requests a reading. This is done
+	 * above in isl29028_set_als_ir_mode() and isl29028_enable_proximity().
+	 */
+	return 0;
+}
+
+static const struct dev_pm_ops isl29028_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(isl29028_suspend, isl29028_resume)
+	SET_RUNTIME_PM_OPS(isl29028_suspend, isl29028_resume, NULL)
+};
+
 static const struct i2c_device_id isl29028_id[] = {
 	{"isl29028", 0},
 	{}
@@ -565,9 +665,11 @@ MODULE_DEVICE_TABLE(of, isl29028_of_match);
 static struct i2c_driver isl29028_driver = {
 	.driver  = {
 		.name = "isl29028",
+		.pm = &isl29028_pm_ops,
 		.of_match_table = isl29028_of_match,
 	},
 	.probe	 = isl29028_probe,
+	.remove  = isl29028_remove,
 	.id_table = isl29028_id,
 };