USB: ssu100: fix overrun-error reporting

commit 75bcbf29 upstream.

Fix reporting of overrun errors, which should only be reported once
using the inserted null character.

Fixes: 6b8f1ca5 ("USB: ssu100: set tty_flags in ssu100_process_packet")
Signed-off-by: Johan Hovold <johan@kernel.org>
[bwh: Backported to 3.2:
 - Use tty_port_tty_get() to look up tty_struct
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/usb/serial/ssu100.c

@@ -599,10 +599,10 @@ static void ssu100_update_lsr(struct usb_serial_port *port, u8 lsr,
 			if (*tty_flag == TTY_NORMAL)
 				*tty_flag = TTY_FRAME;
 		}
-		if (lsr & UART_LSR_OE){
+		if (lsr & UART_LSR_OE) {
 			priv->icount.overrun++;
-			if (*tty_flag == TTY_NORMAL)
-				*tty_flag = TTY_OVERRUN;
+			tty_insert_flip_char(tty_port_tty_get(&port->port),
+					     0, TTY_OVERRUN);
 		}
 	}
 
@@ -623,11 +623,8 @@ static int ssu100_process_packet(struct urb *urb,
 	if ((len >= 4) &&
 	    (packet[0] == 0x1b) && (packet[1] == 0x1b) &&
 	    ((packet[2] == 0x00) || (packet[2] == 0x01))) {
-		if (packet[2] == 0x00) {
+		if (packet[2] == 0x00)
 			ssu100_update_lsr(port, packet[3], &flag);
-			if (flag == TTY_OVERRUN)
-				tty_insert_flip_char(tty, 0, TTY_OVERRUN);
-		}
 		if (packet[2] == 0x01)
 			ssu100_update_msr(port, packet[3]);