The device lm90 can be controlled by the vcc rail.
Adding the regulator support to power on/off the vcc rail.
Enable the "vcc" regulator before accessing the device.

Signed-off-by: Wei Ni <w...@nvidia.com>
---
 drivers/hwmon/lm90.c |   25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/drivers/hwmon/lm90.c b/drivers/hwmon/lm90.c
index cdff742..bd313f4 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/regulator/consumer.h>
+#include <linux/delay.h>
 
 /*
  * Addresses to scan
@@ -302,6 +304,7 @@ 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;
@@ -1397,8 +1400,23 @@ static int lm90_probe(struct i2c_client *client,
        struct device *dev = &client->dev;
        struct i2c_adapter *adapter = to_i2c_adapter(dev->parent);
        struct lm90_data *data;
+       struct regulator *reg;
        int err;
 
+       reg = devm_regulator_get_optional(dev, "vcc");
+       if (!IS_ERR(reg)) {
+               err = regulator_enable(reg);
+               if (err < 0) {
+                       dev_err(&client->dev,
+                               "Failed to enable regulator: %d\n", err);
+                       return err;
+               }
+               msleep(25);
+       } else {
+               if (PTR_ERR(reg) == -EPROBE_DEFER)
+                       return -EPROBE_DEFER;
+       }
+
        data = devm_kzalloc(&client->dev, sizeof(struct lm90_data), GFP_KERNEL);
        if (!data)
                return -ENOMEM;
@@ -1406,6 +1424,8 @@ static int lm90_probe(struct i2c_client *client,
        i2c_set_clientdata(client, data);
        mutex_init(&data->update_lock);
 
+       data->lm90_reg = reg;
+
        /* Set the device type */
        data->kind = id->driver_data;
        if (data->kind == adm1032) {
@@ -1473,6 +1493,9 @@ exit_remove_files:
        lm90_remove_files(client, data);
 exit_restore:
        lm90_restore_conf(client, data);
+       if (!IS_ERR(data->lm90_reg))
+               regulator_disable(data->lm90_reg);
+
        return err;
 }
 
@@ -1483,6 +1506,8 @@ static int lm90_remove(struct i2c_client *client)
        hwmon_device_unregister(data->hwmon_dev);
        lm90_remove_files(client, data);
        lm90_restore_conf(client, data);
+       if (!IS_ERR(data->lm90_reg))
+               regulator_disable(data->lm90_reg);
 
        return 0;
 }
-- 
1.7.9.5

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