diff --git a/drivers/bluetooth/hci_serdev.c b/drivers/bluetooth/hci_serdev.c
index 71664b2..e0e6461 100644
--- a/drivers/bluetooth/hci_serdev.c
+++ b/drivers/bluetooth/hci_serdev.c
@@ -303,6 +303,7 @@ int hci_uart_register_device(struct hci_uart *hu,
 	hci_set_drvdata(hdev, hu);
 
 	INIT_WORK(&hu->write_work, hci_uart_write_work);
+	percpu_init_rwsem(&hu->proto_lock);
 
 	/* Only when vendor specific setup callback is provided, consider
 	 * the manufacturer information valid. This avoids filling in the