diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c
index 038c445a4e9b..a57c36af2786 100644
--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -1150,12 +1150,15 @@ gs_port_alloc(unsigned port_num, struct usb_cdc_line_coding *coding)
 	}
 
 	tty_port_init(&port->port);
+	tty_buffer_set_limit(&port->port, 8388608);
 	spin_lock_init(&port->port_lock);
 	init_waitqueue_head(&port->drain_wait);
 	init_waitqueue_head(&port->close_wait);
 
-	INIT_DELAYED_WORK(&port->push, gs_rx_push);
+	pr_debug("%s open:ttyGS%d and set 8388608, avail:%d\n", __func__,
+		port_num, tty_buffer_space_avail(&port->port));
 
+	INIT_DELAYED_WORK(&port->push, gs_rx_push);
 	INIT_LIST_HEAD(&port->read_pool);
 	INIT_LIST_HEAD(&port->read_queue);
 	INIT_LIST_HEAD(&port->write_pool);