diff --git a/drivers/tty/mxser.c b/drivers/tty/mxser.c
index 71d6eb2c93b1..f97b196693c6 100644
--- a/drivers/tty/mxser.c
+++ b/drivers/tty/mxser.c
@@ -1618,8 +1618,12 @@ static int mxser_ioctl_special(unsigned int cmd, void __user *argp)
 				if (ip->type == PORT_16550A)
 					me->fifo[p] = 1;
 
-				opmode = inb(ip->opmode_ioaddr)>>((p % 4) * 2);
-				opmode &= OP_MODE_MASK;
+				if (ip->board->chip_flag == MOXA_MUST_MU860_HWID) {
+					opmode = inb(ip->opmode_ioaddr)>>((p % 4) * 2);
+					opmode &= OP_MODE_MASK;
+				} else {
+					opmode = RS232_MODE;
+				}
 				me->iftype[p] = opmode;
 				mutex_unlock(&port->mutex);
 			}
@@ -1670,6 +1674,9 @@ static int mxser_ioctl(struct tty_struct *tty,
 		return mxser_ioctl_special(cmd, argp);
 
 	if (cmd == MOXA_SET_OP_MODE || cmd == MOXA_GET_OP_MODE) {
+		if (info->board->chip_flag != MOXA_MUST_MU860_HWID)
+			return -EFAULT;
+
 		int p;
 		unsigned long opmode;
 		static unsigned char ModeMask[] = { 0xfc, 0xf3, 0xcf, 0x3f };