diff --git a/sys/dev/usb/serial/usb_serial.c b/sys/dev/usb/serial/usb_serial.c
index ae4ed3a4339..46d08b5fedb 100644
--- a/sys/dev/usb/serial/usb_serial.c
+++ b/sys/dev/usb/serial/usb_serial.c
@@ -415,8 +415,9 @@ ucom_attach_tty(struct ucom_super_softc *ssc, struct ucom_softc *sc)
 	sc->sc_tty = tp;
 
 	sc->sc_pps.ppscap = PPS_CAPTUREBOTH;
-	sc->sc_pps.mtx = sc->sc_mtx;
-	pps_init(&sc->sc_pps);
+	sc->sc_pps.driver_abi = PPS_ABI_VERSION;
+	sc->sc_pps.driver_mtx = sc->sc_mtx;
+	pps_init_abi(&sc->sc_pps);
 
 	DPRINTF("ttycreate: %s\n", buf);
 
diff --git a/sys/kern/kern_tc.c b/sys/kern/kern_tc.c
index 6264c64e975..9dca0e80e5e 100644
--- a/sys/kern/kern_tc.c
+++ b/sys/kern/kern_tc.c
@@ -1468,6 +1468,17 @@ SYSCTL_PROC(_kern_timecounter, OID_AUTO, choice, CTLTYPE_STRING | CTLFLAG_RD,
  * RFC 2783 PPS-API implementation.
  */
 
+/*
+ *  Return true if the driver is aware of the abi version extensions in the
+ *  pps_state structure, and it supports at least the given abi version number.
+ */
+static inline int
+abi_aware(struct pps_state *pps, int vers)
+{
+
+	return ((pps->kcmode & KCMODE_ABIFLAG) && pps->driver_abi >= vers);
+}
+
 static int
 pps_fetch(struct pps_fetch_args *fapi, struct pps_state *pps)
 {
@@ -1497,10 +1508,17 @@ pps_fetch(struct pps_fetch_args *fapi, struct pps_state *pps)
 		cseq = pps->ppsinfo.clear_sequence;
 		while (aseq == pps->ppsinfo.assert_sequence &&
 		    cseq == pps->ppsinfo.clear_sequence) {
-			if (pps->mtx != NULL)
-				err = msleep(pps, pps->mtx, PCATCH, "ppsfch", timo);
-			else
+			if (abi_aware(pps, 1) && pps->driver_mtx != NULL) {
+				if (pps->flags & PPSFLAG_MTX_SPIN) {
+					err = msleep_spin(pps, pps->driver_mtx,
+					    "ppsfch", timo);
+				} else {
+					err = msleep(pps, pps->driver_mtx, PCATCH,
+					    "ppsfch", timo);
+				}
+			} else {
 				err = tsleep(pps, PCATCH, "ppsfch", timo);
+			}
 			if (err == EWOULDBLOCK && fapi->timeout.tv_sec == -1) {
 				continue;
 			} else if (err != 0) {
@@ -1590,7 +1608,8 @@ pps_ioctl(u_long cmd, caddr_t data, struct pps_state *pps)
 			return (EINVAL);
 		if (kapi->edge & ~pps->ppscap)
 			return (EINVAL);
-		pps->kcmode = kapi->edge;
+		pps->kcmode = (kapi->edge & KCMODE_EDGEMASK) |
+		    (pps->kcmode & KCMODE_ABIFLAG);
 		return (0);
 #else
 		return (EOPNOTSUPP);
@@ -1611,6 +1630,18 @@ pps_init(struct pps_state *pps)
 #ifdef FFCLOCK
 	pps->ppscap |= PPS_TSCLK_MASK;
 #endif
+	pps->kcmode &= ~KCMODE_ABIFLAG;
+}
+
+void
+pps_init_abi(struct pps_state *pps)
+{
+
+	pps_init(pps);
+	if (pps->driver_abi > 0) {
+		pps->kcmode |= KCMODE_ABIFLAG;
+		pps->kernel_abi = PPS_ABI_VERSION;
+	}
 }
 
 void
diff --git a/sys/sys/timepps.h b/sys/sys/timepps.h
index ae4b84d17d7..d472c804dc4 100644
--- a/sys/sys/timepps.h
+++ b/sys/sys/timepps.h
@@ -135,6 +135,13 @@ struct pps_kcbind_args {
 
 struct mtx;
 
+#define	KCMODE_EDGEMASK		0x03
+#define	KCMODE_ABIFLAG		0x80000000 /* Internal use: abi-aware driver. */
+
+#define	PPS_ABI_VERSION		1
+
+#define	PPSFLAG_MTX_SPIN	0x01	/* Driver mtx is MTX_SPIN type. */
+
 struct pps_state {
 	/* Capture information. */
 	struct timehands *capth;
@@ -142,9 +149,6 @@ struct pps_state {
 	unsigned	capgen;
 	unsigned	capcount;
 
-	/* pointer to mutex protecting this state, if any */
-	struct mtx	*mtx;
-
 	/* State information. */
 	pps_params_t	ppsparam;
 	pps_info_t	ppsinfo;
@@ -153,11 +157,19 @@ struct pps_state {
 	int		ppscap;
 	struct timecounter *ppstc;
 	unsigned	ppscount[3];
+	/*
+	 * The following fields are valid if the driver calls pps_init_abi().
+	 */
+	uint16_t	driver_abi;	/* Driver sets before pps_init_abi(). */
+	uint16_t	kernel_abi;	/* Kernel sets during pps_init_abi(). */
+	struct mtx	*driver_mtx;	/* Optional, valid if non-NULL. */
+	uint32_t	flags;
 };
 
 void pps_capture(struct pps_state *pps);
 void pps_event(struct pps_state *pps, int event);
 void pps_init(struct pps_state *pps);
+void pps_init_abi(struct pps_state *pps);
 int pps_ioctl(unsigned long cmd, caddr_t data, struct pps_state *pps);
 void hardpps(struct timespec *tsp, long nsec);