Fix "spurious event" when command ring rolls over

xhci.c: From NetBSD 1.67.

Version 0.20. Tagged as 'XHCIDriver-0_20'

VersionNum

-/* (0.19)
+/* (0.20)
  *
  * This file is automatically maintained by srccommit, do not edit manually.
  * Last processed by srccommit version: 1.1.
  *
  */
-#define Module_MajorVersion_CMHG        0.19
+#define Module_MajorVersion_CMHG        0.20
 #define Module_MinorVersion_CMHG        
 #define Module_Date_CMHG                13 Jul 2017
 
-#define Module_MajorVersion             "0.19"
-#define Module_Version                  19
+#define Module_MajorVersion             "0.20"
+#define Module_Version                  20
 #define Module_MinorVersion             ""
 #define Module_Date                     "13 Jul 2017"
 
@@ -18,6 +18,6 @@
 #define Module_ComponentName            "XHCIDriver"
 #define Module_ComponentPath            "mixed/RiscOS/Sources/HWSupport/USB/Controllers/XHCIDriver"
 
-#define Module_FullVersion              "0.19"
-#define Module_HelpVersion              "0.19 (13 Jul 2017)"
-#define Module_LibraryVersionInfo       "0:19"
+#define Module_FullVersion              "0.20"
+#define Module_HelpVersion              "0.20 (13 Jul 2017)"
+#define Module_LibraryVersionInfo       "0:20"

c/xhci

@@ -1098,7 +1098,7 @@ xhci_configure_endpoint(usbd_pipe_handle pipe)
 
 	/* XXX ensure input context is available? */
 
-	memset(xhci_slot_get_icv(sc, xs, 0), 0, sc->sc_pgsz);
+	memset(xhci_slot_get_icv(sc, xs, XHCI_ICI_INPUT_CONTROL), 0, sc->sc_pgsz);
 
 	cp = xhci_slot_get_icv(sc, xs, XHCI_ICI_INPUT_CONTROL);
 	cp[0] = htole32(0);
@@ -2338,7 +2338,14 @@ xhci_do_command(struct xhci_softc * const sc, struct xhci_trb * const trb,
 #endif
 
 	KASSERT(sc->sc_command_addr == 0);
-	sc->sc_command_addr = xhci_ring_trbp(cr, cr->xr_ep);
+	/*
+	 * If enqueue pointer points at last of ring, it's Link TRB,
+	 * command TRB will be stored in 0th TRB.
+	 */
+	if (cr->xr_ep == cr->xr_ntrb - 1)
+		sc->sc_command_addr = xhci_ring_trbp(cr, 0);
+	else
+		sc->sc_command_addr = xhci_ring_trbp(cr, cr->xr_ep);
 
 	mutex_enter(&cr->xr_lock);
 	xhci_ring_put(sc, cr, NULL, trb, 1);