hwmon: (pmbus) Add new pmbus flag NO_WRITE_PROTECT

Some PMBus chips respond with invalid data when reading the WRITE_PROTECT
register. For such chips, this flag should be set so that the PMBus core
driver doesn't use the WRITE_PROTECT command to determine its behavior.
Signed-off-by: Erik Rosen <erik.rosen@metormote.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/pmbus/pmbus_core.c

@@ -2231,9 +2231,11 @@ static int pmbus_init_common(struct i2c_client *client, struct pmbus_data *data,
 	 * faults, and we should not try it. Also, in that case, writes into
 	 * limit registers need to be disabled.
 	 */
-	ret = i2c_smbus_read_byte_data(client, PMBUS_WRITE_PROTECT);
-	if (ret > 0 && (ret & PB_WP_ANY))
-		data->flags |= PMBUS_WRITE_PROTECTED | PMBUS_SKIP_STATUS_CHECK;
+	if (!(data->flags & PMBUS_NO_WRITE_PROTECT)) {
+		ret = i2c_smbus_read_byte_data(client, PMBUS_WRITE_PROTECT);
+		if (ret > 0 && (ret & PB_WP_ANY))
+			data->flags |= PMBUS_WRITE_PROTECTED | PMBUS_SKIP_STATUS_CHECK;
+	}
 
 	if (data->info->pages)
 		pmbus_clear_faults(client);

include/linux/pmbus.h

@@ -56,6 +56,15 @@
  */
 #define PMBUS_READ_STATUS_AFTER_FAILED_CHECK	BIT(3)
 
+/*
+ * PMBUS_NO_WRITE_PROTECT
+ *
+ * Some PMBus chips respond with invalid data when reading the WRITE_PROTECT
+ * register. For such chips, this flag should be set so that the PMBus core
+ * driver doesn't use the WRITE_PROTECT command to determine its behavior.
+ */
+#define PMBUS_NO_WRITE_PROTECT			BIT(4)
+
 struct pmbus_platform_data {
 	u32 flags;		/* Device specific flags */