Index: sys/dev/gpio/gpiobus.c
===================================================================
--- sys/dev/gpio/gpiobus.c	(revision 221961)
+++ sys/dev/gpio/gpiobus.c	(working copy)
@@ -73,14 +73,13 @@
 static int gpiobus_pin_get(device_t, device_t, uint32_t, unsigned int*);
 static int gpiobus_pin_toggle(device_t, device_t, uint32_t);
 
-#define	GPIOBUS_LOCK(_sc) mtx_lock(&(_sc)->sc_mtx)
-#define	GPIOBUS_UNLOCK(_sc) mtx_unlock(&(_sc)->sc_mtx)
+#define	GPIOBUS_LOCK(_sc) sx_xlock(&(_sc)->sc_sx)
+#define	GPIOBUS_UNLOCK(_sc) sx_xunlock(&(_sc)->sc_sx)
 #define	GPIOBUS_LOCK_INIT(_sc) \
-	mtx_init(&_sc->sc_mtx, device_get_nameunit(_sc->sc_dev), \
-	    "gpiobus", MTX_DEF)
-#define	GPIOBUS_LOCK_DESTROY(_sc) mtx_destroy(&_sc->sc_mtx);
-#define	GPIOBUS_ASSERT_LOCKED(_sc) mtx_assert(&_sc->sc_mtx, MA_OWNED);
-#define	GPIOBUS_ASSERT_UNLOCKED(_sc) mtx_assert(&_sc->sc_mtx, MA_NOTOWNED);
+	sx_init(&_sc->sc_sx, device_get_nameunit(_sc->sc_dev))
+#define	GPIOBUS_LOCK_DESTROY(_sc) sx_destroy(&_sc->sc_sx);
+#define	GPIOBUS_ASSERT_LOCKED(_sc) sx_assert(&_sc->sc_sx, SA_XLOCKED);
+#define	GPIOBUS_ASSERT_UNLOCKED(_sc) sx_assert(&_sc->sc_sx, SA_UNLOCKED);
 
 
 static void
@@ -222,8 +221,6 @@
 	int err, ndevs, i;
 	device_t *devlist;
 
-	KASSERT(mtx_initialized(&sc->sc_mtx),
-	    ("gpiobus mutex not initialized"));
 	GPIOBUS_LOCK_DESTROY(sc);
 
 	if ((err = bus_generic_detach(dev)) != 0)
Index: sys/dev/gpio/gpiobusvar.h
===================================================================
--- sys/dev/gpio/gpiobusvar.h	(revision 221961)
+++ sys/dev/gpio/gpiobusvar.h	(working copy)
@@ -32,14 +32,14 @@
 
 #include <sys/param.h>
 #include <sys/lock.h>
-#include <sys/mutex.h>
+#include <sys/sx.h>
 
 #define GPIOBUS_IVAR(d) (struct gpiobus_ivar *) device_get_ivars(d)
 #define GPIOBUS_SOFTC(d) (struct gpiobus_softc *) device_get_softc(d)
 
 struct gpiobus_softc
 {
-	struct mtx	sc_mtx;		/* bus mutex */
+	struct sx	sc_sx;		/* bus lock */
 	device_t	sc_busdev;	/* bus device */
 	device_t	sc_owner;	/* bus owner */
 	device_t	sc_dev;		/* driver device */