bnxt_en: Add missing periodic PHC overflow check

We use the timecounter APIs for the 48-bit PHC and packet timestamps.
We must periodically update the timecounter at roughly half the
overflow interval.  The overflow interval is about 78 hours, so
update it every 19 hours (1/4 interval) for some extra margins.

Fixes: 390862f4 ("bnxt_en: Get the full 48-bit hardware timestamp periodically")
Reviewed-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c

@@ -353,6 +353,12 @@ static long bnxt_ptp_ts_aux_work(struct ptp_clock_info *ptp_info)
 
 	bnxt_ptp_get_current_time(bp);
 	ptp->next_period = now + HZ;
+	if (time_after_eq(now, ptp->next_overflow_check)) {
+		spin_lock_bh(&ptp->ptp_lock);
+		timecounter_read(&ptp->tc);
+		spin_unlock_bh(&ptp->ptp_lock);
+		ptp->next_overflow_check = now + BNXT_PHC_OVERFLOW_PERIOD;
+	}
 	return HZ;
 }
 
@@ -423,6 +429,7 @@ int bnxt_ptp_init(struct bnxt *bp)
 	ptp->cc.shift = 0;
 	ptp->cc.mult = 1;
 
+	ptp->next_overflow_check = jiffies + BNXT_PHC_OVERFLOW_PERIOD;
 	timecounter_init(&ptp->tc, &ptp->cc, ktime_to_ns(ktime_get_real()));
 
 	ptp->ptp_info = bnxt_ptp_caps;

drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.h

@@ -32,6 +32,10 @@ struct bnxt_ptp_cfg {
 	u64			current_time;
 	u64			old_time;
 	unsigned long		next_period;
+	unsigned long		next_overflow_check;
+	/* 48-bit PHC overflows in 78 hours.  Check overflow every 19 hours. */
+	#define BNXT_PHC_OVERFLOW_PERIOD	(19 * 3600 * HZ)
+
 	u16			tx_seqid;
 	struct bnxt		*bp;
 	atomic_t		tx_avail;