diff --git a/sys/dev/uart/uart_bus.h b/sys/dev/uart/uart_bus.h
index 7394651e841..e78d7697979 100644
--- a/sys/dev/uart/uart_bus.h
+++ b/sys/dev/uart/uart_bus.h
@@ -99,6 +99,7 @@ struct uart_softc {
 	int		sc_polled:1;	/* This UART has no interrupts. */
 	int		sc_txbusy:1;	/* This UART is transmitting. */
 	int		sc_isquelch:1;	/* This UART has input squelched. */
+	int		sc_testintr:1;	/* This UART is under int. testing. */
 
 	struct uart_devinfo *sc_sysdev;	/* System device (or NULL). */
 
@@ -135,7 +136,7 @@ struct uart_softc {
 };
 
 extern devclass_t uart_devclass;
-extern char uart_driver_name[];
+extern const char uart_driver_name[];
 
 int uart_bus_attach(device_t dev);
 int uart_bus_detach(device_t dev);
@@ -157,14 +158,16 @@ void uart_tty_intr(void *arg);
 static __inline int
 uart_rx_empty(struct uart_softc *sc)
 {
+
 	return ((sc->sc_rxget == sc->sc_rxput) ? 1 : 0);
 }
 
 static __inline int
 uart_rx_full(struct uart_softc *sc)
 {
-	return ((sc->sc_rxput + 1 < sc->sc_rxbufsz)
-	    ? (sc->sc_rxput + 1 == sc->sc_rxget) : (sc->sc_rxget == 0));
+
+	return ((sc->sc_rxput + 1 < sc->sc_rxbufsz) ?
+	    (sc->sc_rxput + 1 == sc->sc_rxget) : (sc->sc_rxget == 0));
 }
 
 static __inline int
diff --git a/sys/dev/uart/uart_core.c b/sys/dev/uart/uart_core.c
index 4114f375986..191244a2ae0 100644
--- a/sys/dev/uart/uart_core.c
+++ b/sys/dev/uart/uart_core.c
@@ -52,7 +52,7 @@ __FBSDID("$FreeBSD$");
 #include "uart_if.h"
 
 devclass_t uart_devclass;
-char uart_driver_name[] = "uart";
+const char uart_driver_name[] = "uart";
 
 SLIST_HEAD(uart_devinfo_list, uart_devinfo) uart_sysdevs =
     SLIST_HEAD_INITIALIZER(uart_sysdevs);
@@ -260,13 +260,14 @@ static int
 uart_intr(void *arg)
 {
 	struct uart_softc *sc = arg;
-	int cnt, ipend;
+	int cnt, ipend, testintr;
 
 	if (sc->sc_leaving)
 		return (FILTER_STRAY);
 
 	cnt = 0;
-	while (cnt < 20 && (ipend = UART_IPEND(sc)) != 0) {
+	testintr = sc->sc_testintr;
+	while ((!testintr || cnt < 20) && (ipend = UART_IPEND(sc)) != 0) {
 		cnt++;
 		if (ipend & SER_INT_OVERRUN)
 			uart_intr_overrun(sc);
@@ -277,7 +278,7 @@ uart_intr(void *arg)
 		if (ipend & SER_INT_SIGCHG)
 			uart_intr_sigchg(sc);
 		if (ipend & SER_INT_TXIDLE)
-			uart_intr_txidle(sc);		
+			uart_intr_txidle(sc);
 	}
 
 	if (sc->sc_polled) {
@@ -286,7 +287,8 @@ uart_intr(void *arg)
 	}
 
 	return ((cnt == 0) ? FILTER_STRAY :
-	    ((cnt == 20) ? FILTER_SCHEDULE_THREAD : FILTER_HANDLED));
+	    ((testintr && cnt == 20) ? FILTER_SCHEDULE_THREAD :
+	    FILTER_HANDLED));
 }
 
 serdev_intr_t *
@@ -433,7 +435,7 @@ uart_bus_attach(device_t dev)
 	/*
 	 * Protect ourselves against interrupts while we're not completely
 	 * finished attaching and initializing. We don't expect interrupts
-	 * until after UART_ATTACH() though.
+	 * until after UART_ATTACH(), though.
 	 */
 	sc->sc_leaving = 1;
 
@@ -513,7 +515,9 @@ uart_bus_attach(device_t dev)
 	pps_init(&sc->sc_pps);
 
 	sc->sc_leaving = 0;
+	sc->sc_testintr = 1;
 	filt = uart_intr(sc);
+	sc->sc_testintr = 0;
 
 	/*
 	 * Don't use interrupts if we couldn't clear any pending interrupt