diff --git a/drivers/hwmon/tmp421.c b/drivers/hwmon/tmp421.c
index a94e35c..b963a36 100644
--- a/drivers/hwmon/tmp421.c
+++ b/drivers/hwmon/tmp421.c
@@ -100,70 +100,81 @@
 	s16 temp[4];
 };
 
-static int temp_from_s16(s16 reg)
+static int temp_from_raw(u16 reg, bool extended)
 {
 	/* Mask out status bits */
 	int temp = reg & ~0xf;
 
-	return (temp * 1000 + 128) / 256;
+	if (extended)
+		temp = temp - 64 * 256;
+	else
+		temp = (s16)temp;
+
+	return DIV_ROUND_CLOSEST(temp * 1000, 256);
 }
 
-static int temp_from_u16(u16 reg)
+static int tmp421_update_device(struct tmp421_data *data)
 {
-	/* Mask out status bits */
-	int temp = reg & ~0xf;
-
-	/* Add offset for extended temperature range. */
-	temp -= 64 * 256;
-
-	return (temp * 1000 + 128) / 256;
-}
-
-static struct tmp421_data *tmp421_update_device(struct device *dev)
-{
-	struct tmp421_data *data = dev_get_drvdata(dev);
 	struct i2c_client *client = data->client;
+	int ret = 0;
 	int i;
 
 	mutex_lock(&data->update_lock);
 
-	if (time_after(jiffies, data->last_updated + 2 * HZ) || !data->valid) {
-		data->config = i2c_smbus_read_byte_data(client,
-			TMP421_CONFIG_REG_1);
+	if (time_after(jiffies, data->last_updated + (HZ / 2)) ||
+	    !data->valid) {
+		ret = i2c_smbus_read_byte_data(client, TMP421_CONFIG_REG_1);
+		if (ret < 0)
+			goto exit;
+		data->config = ret;
 
 		for (i = 0; i < data->channels; i++) {
-			data->temp[i] = i2c_smbus_read_byte_data(client,
-				TMP421_TEMP_MSB[i]) << 8;
-			data->temp[i] |= i2c_smbus_read_byte_data(client,
-				TMP421_TEMP_LSB[i]);
+			ret = i2c_smbus_read_byte_data(client, TMP421_TEMP_MSB[i]);
+			if (ret < 0)
+				goto exit;
+			data->temp[i] = ret << 8;
+
+			ret = i2c_smbus_read_byte_data(client, TMP421_TEMP_LSB[i]);
+			if (ret < 0)
+				goto exit;
+			data->temp[i] |= ret;
 		}
 		data->last_updated = jiffies;
 		data->valid = 1;
 	}
 
+exit:
 	mutex_unlock(&data->update_lock);
 
-	return data;
+	if (ret < 0) {
+		data->valid = 0;
+		return ret;
+	}
+
+	return 0;
 }
 
 static int tmp421_read(struct device *dev, enum hwmon_sensor_types type,
 		       u32 attr, int channel, long *val)
 {
-	struct tmp421_data *tmp421 = tmp421_update_device(dev);
+	struct tmp421_data *tmp421 = dev_get_drvdata(dev);
+	int ret = 0;
+
+	ret = tmp421_update_device(tmp421);
+	if (ret)
+		return ret;
 
 	switch (attr) {
 	case hwmon_temp_input:
-		if (tmp421->config & TMP421_CONFIG_RANGE)
-			*val = temp_from_u16(tmp421->temp[channel]);
-		else
-			*val = temp_from_s16(tmp421->temp[channel]);
+		*val = temp_from_raw(tmp421->temp[channel],
+				     tmp421->config & TMP421_CONFIG_RANGE);
 		return 0;
 	case hwmon_temp_fault:
 		/*
-		 * The OPEN bit signals a fault. This is bit 0 of the temperature
-		 * register (low byte).
+		 * Any of OPEN or /PVLD bits indicate a hardware mulfunction
+		 * and the conversion result may be incorrect
 		 */
-		*val = tmp421->temp[channel] & 0x01;
+		*val = !!(tmp421->temp[channel] & 0x03);
 		return 0;
 	default:
 		return -EOPNOTSUPP;
@@ -176,9 +187,6 @@
 {
 	switch (attr) {
 	case hwmon_temp_fault:
-		if (channel == 0)
-			return 0;
-		return 0444;
 	case hwmon_temp_input:
 		return 0444;
 	default:
@@ -278,8 +286,7 @@
 	.read = tmp421_read,
 };
 
-static int tmp421_probe(struct i2c_client *client,
-			const struct i2c_device_id *id)
+static int tmp421_probe(struct i2c_client *client)
 {
 	struct device *dev = &client->dev;
 	struct device *hwmon_dev;
@@ -295,7 +302,7 @@
 		data->channels = (unsigned long)
 			of_device_get_match_data(&client->dev);
 	else
-		data->channels = id->driver_data;
+		data->channels = i2c_match_id(tmp421_id, client)->driver_data;
 	data->client = client;
 
 	err = tmp421_init_client(client);
@@ -326,7 +333,7 @@
 		.name	= "tmp421",
 		.of_match_table = of_match_ptr(tmp421_of_match),
 	},
-	.probe = tmp421_probe,
+	.probe_new = tmp421_probe,
 	.id_table = tmp421_id,
 	.detect = tmp421_detect,
 	.address_list = normal_i2c,