ptp: ocp: adjust utc_tai_offset to TOD info

utc_tai_offset is used to correct IRIG, DCF and NMEA outputs and is
set during initialisation but is not corrected during leap second
announce event.  Add watchdog code to control this correction.
Signed-off-by: Vadim Fedorenko <vadfed@fb.com>
Signed-off-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/ptp/ptp_ocp.c

@@ -741,12 +741,31 @@ __ptp_ocp_clear_drift_locked(struct ptp_ocp *bp)
 	iowrite32(select >> 16, &bp->reg->select);
 }
 
+static void
+ptp_ocp_utc_distribute(struct ptp_ocp *bp, u32 val)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&bp->lock, flags);
+
+	bp->utc_tai_offset = val;
+
+	if (bp->irig_out)
+		iowrite32(val, &bp->irig_out->adj_sec);
+	if (bp->dcf_out)
+		iowrite32(val, &bp->dcf_out->adj_sec);
+	if (bp->nmea_out)
+		iowrite32(val, &bp->nmea_out->adj_sec);
+
+	spin_unlock_irqrestore(&bp->lock, flags);
+}
+
 static void
 ptp_ocp_watchdog(struct timer_list *t)
 {
 	struct ptp_ocp *bp = from_timer(bp, t, watchdog);
 	unsigned long flags;
-	u32 status;
+	u32 status, utc_offset;
 
 	status = ioread32(&bp->pps_to_clk->status);
 
@@ -763,6 +782,17 @@ ptp_ocp_watchdog(struct timer_list *t)
 		bp->gnss_lost = 0;
 	}
 
+	/* if GNSS provides correct data we can rely on
+	 * it to get leap second information
+	 */
+	if (bp->tod) {
+		status = ioread32(&bp->tod->utc_status);
+		utc_offset = status & TOD_STATUS_UTC_MASK;
+		if (status & TOD_STATUS_UTC_VALID &&
+		    utc_offset != bp->utc_tai_offset)
+			ptp_ocp_utc_distribute(bp, utc_offset);
+	}
+
 	mod_timer(&bp->watchdog, jiffies + HZ);
 }
 
@@ -831,25 +861,6 @@ ptp_ocp_init_clock(struct ptp_ocp *bp)
 	return 0;
 }
 
-static void
-ptp_ocp_utc_distribute(struct ptp_ocp *bp, u32 val)
-{
-	unsigned long flags;
-
-	spin_lock_irqsave(&bp->lock, flags);
-
-	bp->utc_tai_offset = val;
-
-	if (bp->irig_out)
-		iowrite32(val, &bp->irig_out->adj_sec);
-	if (bp->dcf_out)
-		iowrite32(val, &bp->dcf_out->adj_sec);
-	if (bp->nmea_out)
-		iowrite32(val, &bp->nmea_out->adj_sec);
-
-	spin_unlock_irqrestore(&bp->lock, flags);
-}
-
 static void
 ptp_ocp_tod_init(struct ptp_ocp *bp)
 {