[PATCH 1/2] hwmon: (lm90) Add power control

[Wei Ni <wni@nvidia.com>]

The device lm90 can be controlled by the vdd rail.
Adding the power control support to power on/off the vdd rail.
And make sure that power is enabled before accessing the device.

Signed-off-by: Wei Ni <wni@nvidia.com>
---
 drivers/hwmon/lm90.c |   52 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)

diff --git a/drivers/hwmon/lm90.c b/drivers/hwmon/lm90.c
index cdff742..eeb0115 100644
--- a/drivers/hwmon/lm90.c
+++ b/drivers/hwmon/lm90.c
@@ -89,6 +89,8 @@
 #include <linux/err.h>
 #include <linux/mutex.h>
 #include <linux/sysfs.h>
+#include <linux/delay.h>
+#include <linux/regulator/consumer.h>
 
 /*
  * Addresses to scan
@@ -179,6 +181,8 @@ enum chips { lm90, adm1032, lm99, lm86, max6657, max6659, adt7461, max6680,
 #define LM90_HAVE_TEMP3		(1 << 6) /* 3rd temperature sensor	*/
 #define LM90_HAVE_BROKEN_ALERT	(1 << 7) /* Broken alert		*/
 
+#define POWER_ON_DELAY 20 /*ms*/
+
 /*
  * Driver data (common to all clients)
  */
@@ -302,6 +306,7 @@ static const struct lm90_params lm90_params[] = {
 struct lm90_data {
 	struct device *hwmon_dev;
 	struct mutex update_lock;
+	struct regulator *lm90_reg;
 	char valid; /* zero until following fields are valid */
 	unsigned long last_updated; /* in jiffies */
 	int kind;
@@ -1391,6 +1396,48 @@ static void lm90_init_client(struct i2c_client *client)
 		i2c_smbus_write_byte_data(client, LM90_REG_W_CONFIG1, config);
 }
 
+static int lm90_power_control(struct i2c_client *client, bool is_enable)
+{
+	struct lm90_data *data = i2c_get_clientdata(client);
+	int ret;
+
+	mutex_lock(&data->update_lock);
+
+	if (!data->lm90_reg) {
+		data->lm90_reg = regulator_get(&client->dev, "vdd");
+		if (IS_ERR_OR_NULL(data->lm90_reg)) {
+			if (PTR_ERR(data->lm90_reg) == -ENODEV)
+				dev_info(&client->dev,
+					 "No regulator found for vdd. Assuming vdd is always powered.");
+			else
+				dev_warn(&client->dev,
+					 "Error [%ld] in getting the regulator handle for vdd.\n",
+					 PTR_ERR(data->lm90_reg));
+			data->lm90_reg = NULL;
+			mutex_unlock(&data->update_lock);
+			return -ENODEV;
+		}
+	}
+	if (is_enable) {
+		ret = regulator_enable(data->lm90_reg);
+		msleep(POWER_ON_DELAY);
+	} else {
+		ret = regulator_disable(data->lm90_reg);
+	}
+
+	if (ret < 0)
+		dev_err(&client->dev,
+			"Error in %s rail vdd, error %d\n",
+			(is_enable) ? "enabling" : "disabling", ret);
+	else
+		dev_info(&client->dev, "success in %s rail vdd\n",
+			 (is_enable) ? "enabling" : "disabling");
+
+	mutex_unlock(&data->update_lock);
+
+	return ret;
+}
+
 static int lm90_probe(struct i2c_client *client,
 		      const struct i2c_device_id *id)
 {
@@ -1406,6 +1453,10 @@ static int lm90_probe(struct i2c_client *client,
 	i2c_set_clientdata(client, data);
 	mutex_init(&data->update_lock);
 
+	err = lm90_power_control(client, true);
+	if (err < 0)
+		return err;
+
 	/* Set the device type */
 	data->kind = id->driver_data;
 	if (data->kind == adm1032) {
@@ -1483,6 +1534,7 @@ static int lm90_remove(struct i2c_client *client)
 	hwmon_device_unregister(data->hwmon_dev);
 	lm90_remove_files(client, data);
 	lm90_restore_conf(client, data);
+	lm90_power_control(client, false);
 
 	return 0;
 }
-- 
1.7.9.5