iio: tsl2583: add runtime power management support

This patch adds runtime power management support to the tsl2583 driver.
The device is powered off after two seconds of inactivity. Verified that
the driver still functions correctly using a TSL2581 hooked up to a
Raspberry Pi 2.

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

drivers/iio/light/tsl2583.c

@@ -3,7 +3,7 @@
  * within the TAOS tsl258x family of devices (tsl2580, tsl2581, tsl2583).
  *
  * Copyright (c) 2011, TAOS Corporation.
- * Copyright (c) 2016 Brian Masney <masneyb@onstation.org>
+ * Copyright (c) 2016-2017 Brian Masney <masneyb@onstation.org>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -27,6 +27,7 @@
 #include <linux/module.h>
 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>
+#include <linux/pm_runtime.h>
 
 /* Device Registers and Masks */
 #define TSL2583_CNTRL			0x00
@@ -64,6 +65,8 @@
 #define TSL2583_CHIP_ID			0x90
 #define TSL2583_CHIP_ID_MASK		0xf0
 
+#define TSL2583_POWER_OFF_DELAY_MS	2000
+
 /* Per-device data */
 struct tsl2583_als_info {
 	u16 als_ch0;
@@ -108,7 +111,6 @@ struct tsl2583_chip {
 	struct tsl2583_settings als_settings;
 	int als_time_scale;
 	int als_saturation;
-	bool suspended;
 };
 
 struct gainadj {
@@ -460,8 +462,6 @@ static int tsl2583_chip_init_and_power_on(struct iio_dev *indio_dev)
 	if (ret < 0)
 		return ret;
 
-	chip->suspended = false;
-
 	return ret;
 }
 
@@ -513,11 +513,6 @@ static ssize_t in_illuminance_calibrate_store(struct device *dev,
 
 	mutex_lock(&chip->als_mutex);
 
-	if (chip->suspended) {
-		ret = -EBUSY;
-		goto done;
-	}
-
 	ret = tsl2583_als_calibrate(indio_dev);
 	if (ret < 0)
 		goto done;
@@ -645,20 +640,36 @@ static const struct iio_chan_spec tsl2583_channels[] = {
 	},
 };
 
+static int tsl2583_set_pm_runtime_busy(struct tsl2583_chip *chip, bool on)
+{
+	int ret;
+
+	if (on) {
+		ret = pm_runtime_get_sync(&chip->client->dev);
+		if (ret < 0)
+			pm_runtime_put_noidle(&chip->client->dev);
+	} else {
+		pm_runtime_mark_last_busy(&chip->client->dev);
+		ret = pm_runtime_put_autosuspend(&chip->client->dev);
+	}
+
+	return ret;
+}
+
 static int tsl2583_read_raw(struct iio_dev *indio_dev,
 			    struct iio_chan_spec const *chan,
 			    int *val, int *val2, long mask)
 {
 	struct tsl2583_chip *chip = iio_priv(indio_dev);
-	int ret = -EINVAL;
+	int ret, pm_ret;
 
-	mutex_lock(&chip->als_mutex);
+	ret = tsl2583_set_pm_runtime_busy(chip, true);
+	if (ret < 0)
+		return ret;
 
-	if (chip->suspended) {
-		ret = -EBUSY;
-		goto read_done;
-	}
+	mutex_lock(&chip->als_mutex);
 
+	ret = -EINVAL;
 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
 		if (chan->type == IIO_LIGHT) {
@@ -719,6 +730,18 @@ static int tsl2583_read_raw(struct iio_dev *indio_dev,
 read_done:
 	mutex_unlock(&chip->als_mutex);
 
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * Preserve the ret variable if the call to
+	 * tsl2583_set_pm_runtime_busy() is successful so the reading
+	 * (if applicable) is returned to user space.
+	 */
+	pm_ret = tsl2583_set_pm_runtime_busy(chip, false);
+	if (pm_ret < 0)
+		return pm_ret;
+
 	return ret;
 }
 
@@ -727,15 +750,15 @@ static int tsl2583_write_raw(struct iio_dev *indio_dev,
 			     int val, int val2, long mask)
 {
 	struct tsl2583_chip *chip = iio_priv(indio_dev);
-	int ret = -EINVAL;
+	int ret;
 
-	mutex_lock(&chip->als_mutex);
+	ret = tsl2583_set_pm_runtime_busy(chip, true);
+	if (ret < 0)
+		return ret;
 
-	if (chip->suspended) {
-		ret = -EBUSY;
-		goto write_done;
-	}
+	mutex_lock(&chip->als_mutex);
 
+	ret = -EINVAL;
 	switch (mask) {
 	case IIO_CHAN_INFO_CALIBBIAS:
 		if (chan->type == IIO_LIGHT) {
@@ -767,9 +790,15 @@ static int tsl2583_write_raw(struct iio_dev *indio_dev,
 		break;
 	}
 
-write_done:
 	mutex_unlock(&chip->als_mutex);
 
+	if (ret < 0)
+		return ret;
+
+	ret = tsl2583_set_pm_runtime_busy(chip, false);
+	if (ret < 0)
+		return ret;
+
 	return ret;
 }
 
@@ -803,7 +832,6 @@ static int tsl2583_probe(struct i2c_client *clientp,
 	i2c_set_clientdata(clientp, indio_dev);
 
 	mutex_init(&chip->als_mutex);
-	chip->suspended = true;
 
 	ret = i2c_smbus_read_byte_data(clientp,
 				       TSL2583_CMD_REG | TSL2583_CHIPID);
@@ -826,6 +854,11 @@ static int tsl2583_probe(struct i2c_client *clientp,
 	indio_dev->modes = INDIO_DIRECT_MODE;
 	indio_dev->name = chip->client->name;
 
+	pm_runtime_enable(&clientp->dev);
+	pm_runtime_set_autosuspend_delay(&clientp->dev,
+					 TSL2583_POWER_OFF_DELAY_MS);
+	pm_runtime_use_autosuspend(&clientp->dev);
+
 	ret = devm_iio_device_register(indio_dev->dev.parent, indio_dev);
 	if (ret) {
 		dev_err(&clientp->dev, "%s: iio registration failed\n",
@@ -836,16 +869,25 @@ static int tsl2583_probe(struct i2c_client *clientp,
 	/* Load up the V2 defaults (these are hard coded defaults for now) */
 	tsl2583_defaults(chip);
 
-	/* Make sure the chip is on */
-	ret = tsl2583_chip_init_and_power_on(indio_dev);
-	if (ret < 0)
-		return ret;
-
 	dev_info(&clientp->dev, "Light sensor found.\n");
 
 	return 0;
 }
 
+static int tsl2583_remove(struct i2c_client *client)
+{
+	struct iio_dev *indio_dev = i2c_get_clientdata(client);
+	struct tsl2583_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 tsl2583_set_power_state(chip, TSL2583_CNTL_PWR_OFF);
+}
+
 static int __maybe_unused tsl2583_suspend(struct device *dev)
 {
 	struct iio_dev *indio_dev = i2c_get_clientdata(to_i2c_client(dev));
@@ -855,7 +897,6 @@ static int __maybe_unused tsl2583_suspend(struct device *dev)
 	mutex_lock(&chip->als_mutex);
 
 	ret = tsl2583_set_power_state(chip, TSL2583_CNTL_PWR_OFF);
-	chip->suspended = true;
 
 	mutex_unlock(&chip->als_mutex);
 
@@ -877,7 +918,11 @@ static int __maybe_unused tsl2583_resume(struct device *dev)
 	return ret;
 }
 
-static SIMPLE_DEV_PM_OPS(tsl2583_pm_ops, tsl2583_suspend, tsl2583_resume);
+static const struct dev_pm_ops tsl2583_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
+				pm_runtime_force_resume)
+	SET_RUNTIME_PM_OPS(tsl2583_suspend, tsl2583_resume, NULL)
+};
 
 static struct i2c_device_id tsl2583_idtable[] = {
 	{ "tsl2580", 0 },
@@ -904,6 +949,7 @@ static struct i2c_driver tsl2583_driver = {
 	},
 	.id_table = tsl2583_idtable,
 	.probe = tsl2583_probe,
+	.remove = tsl2583_remove,
 };
 module_i2c_driver(tsl2583_driver);