hwmon: (pmbus/mp2975) Add error check for pmbus_read_word_data() return value

mp2973_read_word_data() XORs the return value of pmbus_read_word_data()
with PB_STATUS_POWER_GOOD_N without first checking for errors. If the I2C
transaction fails, a negative error code is XORed with the constant,
producing a corrupted value that is returned as valid status data instead
of propagating the error.

Add the missing error check before modifying the return value.

Fixes: acda945 ("hwmon: (pmbus/mp2975) Fix PGOOD in READ_STATUS_WORD")
Cc: [email protected]
Signed-off-by: Sanman Pradhan <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Guenter Roeck <[email protected]>

Author: Sanman Pradhan

drivers/hwmon/pmbus/mp2975.c

@@ -313,6 +313,8 @@ static int mp2973_read_word_data(struct i2c_client *client, int page,
 	case PMBUS_STATUS_WORD:
 		/* MP2973 & MP2971 return PGOOD instead of PB_STATUS_POWER_GOOD_N. */
 		ret = pmbus_read_word_data(client, page, phase, reg);
+		if (ret < 0)
+			return ret;
 		ret ^= PB_STATUS_POWER_GOOD_N;
 		break;
 	case PMBUS_OT_FAULT_LIMIT: