Index: sys/powerpc/powermac/smu.c
===================================================================
--- sys/powerpc/powermac/smu.c
+++ sys/powerpc/powermac/smu.c
@@ -108,6 +108,7 @@
 
 struct smu_softc {
 	device_t	sc_dev;
+	device_t	sc_doorbell;
 	struct mtx	sc_mtx;
 
 	struct resource	*sc_memr;
@@ -181,8 +182,6 @@
 
 /* where to find the doorbell GPIO */
 
-static device_t	smu_doorbell = NULL;
-
 static device_method_t  smu_methods[] = {
 	/* Device interface */
 	DEVMETHOD(device_probe,		smu_probe),
@@ -278,6 +277,49 @@
 	sc->sc_cmd_phys = segs[0].ds_addr;
 }
 
+static void
+smu_setup_intr(device_t smu, device_t doorbell)
+{
+	struct smu_softc *sc;
+	static device_t	doorbell_dev = NULL;
+	static device_t smu_dev = NULL;
+
+	/*
+	 * Defer establishing the interrupt until both devices are ready.
+	 */
+	if (smu != NULL)
+		smu_dev = smu;
+	if (doorbell != NULL)
+		doorbell_dev = doorbell;
+	if (smu_dev == NULL || doorbell_dev == NULL)
+		return;
+
+	/*
+	 * Set up doorbell interrupt.
+	 */
+	sc = device_get_softc(smu);
+	sc->sc_doorbell = doorbell_dev;
+	sc->sc_doorbellirqid = 0;
+	sc->sc_doorbellirq = bus_alloc_resource_any(doorbell_dev, SYS_RES_IRQ,
+	    &sc->sc_doorbellirqid, RF_ACTIVE);
+	bus_setup_intr(doorbell, sc->sc_doorbellirq,
+	    INTR_TYPE_MISC | INTR_MPSAFE, NULL, smu_doorbell_intr, smu_dev,
+	    &sc->sc_doorbellirqcookie);
+	powerpc_config_intr(rman_get_start(sc->sc_doorbellirq),
+	    INTR_TRIGGER_EDGE, INTR_POLARITY_LOW);
+
+	/*
+	 * Connect RTC interface.
+	 */
+	clock_register(smu_dev, 1000);
+
+	/*
+	 * Learn about shutdown events
+	 */
+	EVENTHANDLER_REGISTER(shutdown_final, smu_shutdown, smu_dev,
+	    SHUTDOWN_PRI_LAST);
+}
+
 static int
 smu_attach(device_t dev)
 {
@@ -379,28 +421,7 @@
 	    "server_mode", CTLTYPE_INT | CTLFLAG_RW, dev, 0,
 	    smu_server_mode, "I", "Enable reboot after power failure");
 
-	/*
-	 * Set up doorbell interrupt.
-	 */
-	sc->sc_doorbellirqid = 0;
-	sc->sc_doorbellirq = bus_alloc_resource_any(smu_doorbell, SYS_RES_IRQ,
-	    &sc->sc_doorbellirqid, RF_ACTIVE);
-	bus_setup_intr(smu_doorbell, sc->sc_doorbellirq,
-	    INTR_TYPE_MISC | INTR_MPSAFE, NULL, smu_doorbell_intr, dev,
-	    &sc->sc_doorbellirqcookie);
-	powerpc_config_intr(rman_get_start(sc->sc_doorbellirq),
-	    INTR_TRIGGER_EDGE, INTR_POLARITY_LOW);
-
-	/*
-	 * Connect RTC interface.
-	 */
-	clock_register(dev, 1000);
-
-	/*
-	 * Learn about shutdown events
-	 */
-	EVENTHANDLER_REGISTER(shutdown_final, smu_shutdown, dev,
-	    SHUTDOWN_PRI_LAST);
+	smu_setup_intr(dev, NULL);
 
 	return (bus_generic_attach(dev));
 }
@@ -420,6 +441,8 @@
 	sc = device_get_softc(dev);
 
 	mtx_assert(&sc->sc_mtx, MA_OWNED);
+	/* Should always have a doorbell dev to get here */
+	KASSERT(sc->sc_doorbell != NULL, "Missing doorbell device");
 
 	if (sc->sc_u3)
 		powerpc_pow_enabled = 0; /* SMU cannot work if we go to NAP */
@@ -437,7 +460,7 @@
 	__asm __volatile("sync; dcbf 0,%0; sync" :: "r"(sc->sc_cmd): "memory");
 
 	/* Ring SMU doorbell */
-	macgpio_write(smu_doorbell, GPIO_DDR_OUTPUT);
+	macgpio_write(sc->sc_doorbell, GPIO_DDR_OUTPUT);
 }
 
 static void
@@ -448,8 +471,8 @@
 	int doorbell_ack;
 
 	smu = xdev;
-	doorbell_ack = macgpio_read(smu_doorbell);
 	sc = device_get_softc(smu);
+	doorbell_ack = macgpio_read(sc->sc_doorbell);
 
 	if (doorbell_ack != (GPIO_DDR_OUTPUT | GPIO_LEVEL_RO | GPIO_DATA)) 
 		return;
@@ -648,7 +671,7 @@
 static int
 doorbell_attach(device_t dev)
 {
-	smu_doorbell = dev;
+	smu_setup_intr(NULL, dev);
 	return (0);
 }