hwmon: (pmbus/mpq8785) fix VOUT_MODE mismatch during identification

When MPQ8785 reports VOUT_MODE as VID mode, mpq8785_identify()
configures the driver for direct mode. The subsequent
pmbus_identify_common() check then fails due to a mismatch
between the reported mode and the configured mode, causing
device initialization to fail.

Override the reported VOUT_MODE to direct mode to keep the
driver configuration consistent with the reported mode and
allow successful device initialization.

This does not change how voltages are interpreted, but avoids
a false identification failure caused by mismatched mode
handling.

Fixes: f20b4a9 ("hwmon: Add driver for MPS MPQ8785 Synchronous Step-Down Converter")
Signed-off-by: Carl Lee <carl.lee@amd.com>
Link: https://lore.kernel.org/r/20260210-dt-bindings-hwmon-pmbus-mpq8785-add-mpq8786-support-v3-1-84636ccfe76f@amd.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Author: carl-lee-amd

drivers/hwmon/pmbus/mpq8785.c

@@ -47,6 +47,33 @@ static int mpq8785_identify(struct i2c_client *client,
 	return 0;
 };
 
+static int mpq8785_read_byte_data(struct i2c_client *client, int page, int reg)
+{
+	int ret;
+
+	switch (reg) {
+	case PMBUS_VOUT_MODE:
+		ret = pmbus_read_byte_data(client, page, reg);
+		if (ret < 0)
+			return ret;
+
+		if ((ret >> 5) == 1) {
+			/*
+			 * The MPQ8785 chip reports VOUT_MODE as VID mode, but the driver
+			 * treats VID as direct mode. Without this, identification would fail
+			 * due to mode mismatch.
+			 * This override ensures the reported mode matches the driver
+			 * configuration, allowing successful initialization.
+			 */
+			return PB_VOUT_MODE_DIRECT;
+		}
+
+		return ret;
+	default:
+		return -ENODATA;
+	}
+}
+
 static int mpm82504_read_word_data(struct i2c_client *client, int page,
 				   int phase, int reg)
 {
@@ -129,6 +156,7 @@ static int mpq8785_probe(struct i2c_client *client)
 		break;
 	case mpq8785:
 		info->identify = mpq8785_identify;
+		info->read_byte_data = mpq8785_read_byte_data;
 		break;
 	default:
 		return -ENODEV;