FreeBSD PPS echo patch

--- sys/dev/ppbus/pps.c	2017-07-21 01:41:50.000000000 +0200
+++ sys/dev/ppbus/pps.c	2018-05-18 21:43:59.705177000 +0200
@@ -46,6 +46,7 @@ struct pps_data {
 	device_t ppbus;
 	int	busy;
 	struct callout timeout;
+	struct callout timeout_pulse;
 	int	lastdata;
 
 	struct sx lock;
@@ -132,6 +133,7 @@ ppsattach(device_t dev)
 
 	sx_init(&sc->lock, "pps");
 	ppb_init_callout(ppbus, &sc->timeout, 0);
+	callout_init(&sc->timeout_pulse, 1);
 	sc->ppsdev = dev;
 	sc->ppbus = ppbus;
 	unit = device_get_unit(ppbus);
@@ -297,6 +299,13 @@ ppshcpoll(void *arg)
 }
 
 static void
+ppsintr_callout(void *arg)
+{
+	struct pps_data *sc = (struct pps_data *)arg;
+	ppb_wctr(sc->ppbus, IRQENABLE);
+}
+
+static void
 ppsintr(void *arg)
 {
 	struct pps_data *sc = (struct pps_data *)arg;
@@ -306,11 +315,13 @@ ppsintr(void *arg)
 	if (!(ppb_rstr(sc->ppbus) & nACK))
 		return;
 
-	if (sc->pps[0].ppsparam.mode & PPS_ECHOASSERT)
+	if (sc->pps[0].ppsparam.mode & PPS_ECHOASSERT) {
 		ppb_wctr(sc->ppbus, IRQENABLE | AUTOFEED);
+	}
 	pps_event(&sc->pps[0], PPS_CAPTUREASSERT);
-	if (sc->pps[0].ppsparam.mode & PPS_ECHOASSERT)
-		ppb_wctr(sc->ppbus, IRQENABLE);
+	if (sc->pps[0].ppsparam.mode & PPS_ECHOASSERT) {
+		callout_reset(&sc->timeout_pulse, hz/5, ppsintr_callout, sc);
+	}
 }
 
 static int