hwmon: (pmbus/core) Add lock and unlock functions

Debugfs operations may set the page number, which must be done
atomically with the subsequent i2c operation. Lock the update_lock
in the debugfs functions and provide a function for pmbus drivers
to lock and unlock the update_lock.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Link: https://lore.kernel.org/r/20230412161526.252294-2-eajames@linux.ibm.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Author: Eddie James

drivers/hwmon/pmbus/pmbus.h

@@ -505,6 +505,8 @@ int pmbus_get_fan_rate_device(struct i2c_client *client, int page, int id,
 			      enum pmbus_fan_mode mode);
 int pmbus_get_fan_rate_cached(struct i2c_client *client, int page, int id,
 			      enum pmbus_fan_mode mode);
+int pmbus_lock_interruptible(struct i2c_client *client);
+void pmbus_unlock(struct i2c_client *client);
 int pmbus_update_fan(struct i2c_client *client, int page, int id,
 		     u8 config, u8 mask, u16 command);
 struct dentry *pmbus_get_debugfs_dir(struct i2c_client *client);

drivers/hwmon/pmbus/pmbus_core.c

@@ -3263,8 +3263,13 @@ static int pmbus_debugfs_get(void *data, u64 *val)
 {
 	int rc;
 	struct pmbus_debugfs_entry *entry = data;
+	struct pmbus_data *pdata = i2c_get_clientdata(entry->client);
 
+	rc = mutex_lock_interruptible(&pdata->update_lock);
+	if (rc)
+		return rc;
 	rc = _pmbus_read_byte_data(entry->client, entry->page, entry->reg);
+	mutex_unlock(&pdata->update_lock);
 	if (rc < 0)
 		return rc;
 
@@ -3281,7 +3286,11 @@ static int pmbus_debugfs_get_status(void *data, u64 *val)
 	struct pmbus_debugfs_entry *entry = data;
 	struct pmbus_data *pdata = i2c_get_clientdata(entry->client);
 
+	rc = mutex_lock_interruptible(&pdata->update_lock);
+	if (rc)
+		return rc;
 	rc = pdata->read_status(entry->client, entry->page);
+	mutex_unlock(&pdata->update_lock);
 	if (rc < 0)
 		return rc;
 
@@ -3297,10 +3306,15 @@ static ssize_t pmbus_debugfs_mfr_read(struct file *file, char __user *buf,
 {
 	int rc;
 	struct pmbus_debugfs_entry *entry = file->private_data;
+	struct pmbus_data *pdata = i2c_get_clientdata(entry->client);
 	char data[I2C_SMBUS_BLOCK_MAX + 2] = { 0 };
 
+	rc = mutex_lock_interruptible(&pdata->update_lock);
+	if (rc)
+		return rc;
 	rc = pmbus_read_block_data(entry->client, entry->page, entry->reg,
 				   data);
+	mutex_unlock(&pdata->update_lock);
 	if (rc < 0)
 		return rc;
 
@@ -3638,6 +3652,22 @@ struct dentry *pmbus_get_debugfs_dir(struct i2c_client *client)
 }
 EXPORT_SYMBOL_NS_GPL(pmbus_get_debugfs_dir, PMBUS);
 
+int pmbus_lock_interruptible(struct i2c_client *client)
+{
+	struct pmbus_data *data = i2c_get_clientdata(client);
+
+	return mutex_lock_interruptible(&data->update_lock);
+}
+EXPORT_SYMBOL_NS_GPL(pmbus_lock_interruptible, PMBUS);
+
+void pmbus_unlock(struct i2c_client *client)
+{
+	struct pmbus_data *data = i2c_get_clientdata(client);
+
+	mutex_unlock(&data->update_lock);
+}
+EXPORT_SYMBOL_NS_GPL(pmbus_unlock, PMBUS);
+
 static int __init pmbus_core_init(void)
 {
 	pmbus_debugfs_dir = debugfs_create_dir("pmbus", NULL);