=== xhci.h
==================================================================
--- xhci.h	(revision 252698)
+++ xhci.h	(local)
@@ -438,6 +438,8 @@
 	/* configure message */
 	struct usb_bus_msg	sc_config_msg[2];
 
+	struct usb_callout	sc_callout;
+
 	union xhci_hub_desc	sc_hub_desc;
 
 	struct cv		sc_cmd_cv;
=== xhci_pci.c
==================================================================
--- xhci_pci.c	(revision 252698)
+++ xhci_pci.c	(local)
@@ -142,6 +142,16 @@
 	usb_callout_reset(&sc->sc_callout, 1, (void *)&xhci_interrupt_poll, sc);
 }
 
+static void
+xhci_timer(void *_sc)
+{
+	struct xhci_softc *sc = _sc;
+	USB_BUS_UNLOCK(&sc->sc_bus);
+	xhci_interrupt(sc);
+	USB_BUS_LOCK(&sc->sc_bus);
+	usb_callout_reset(&sc->sc_callout, 1, (void *)&xhci_timer, sc);
+}
+
 static int
 xhci_pci_attach(device_t self)
 {
@@ -186,6 +196,12 @@
 
 	sprintf(sc->sc_vendor, "0x%04x", pci_get_vendor(self));
 
+	usb_callout_init_mtx(&sc->sc_callout, &sc->sc_bus.bus_mtx, 0);
+
+	USB_BUS_LOCK(&sc->sc_bus);
+	xhci_timer(sc);
+	USB_BUS_UNLOCK(&sc->sc_bus);
+
 	if (sc->sc_irq_res != NULL) {
 		err = bus_setup_intr(self, sc->sc_irq_res, INTR_TYPE_BIO | INTR_MPSAFE,
 		    NULL, (driver_intr_t *)xhci_interrupt, sc, &sc->sc_intr_hdl);