net: stmmac: avoid using timespec

We want to deprecate the use of 'struct timespec' on 32-bit
architectures, as it is will overflow in 2038. The stmmac
driver uses it to read the current time, and can simply
be changed to use ktime_get_real_ts64() instead.

Because of hardware limitations, there is still an overflow
in year 2106, which we cannot really avoid, but this documents
the overflow.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -424,7 +424,7 @@ static int stmmac_hwtstamp_ioctl(struct net_device *dev, struct ifreq *ifr)
 {
 	struct stmmac_priv *priv = netdev_priv(dev);
 	struct hwtstamp_config config;
-	struct timespec now;
+	struct timespec64 now;
 	u64 temp = 0;
 	u32 ptp_v2 = 0;
 	u32 tstamp_all = 0;
@@ -621,8 +621,10 @@ static int stmmac_hwtstamp_ioctl(struct net_device *dev, struct ifreq *ifr)
 					     priv->default_addend);
 
 		/* initialize system time */
-		getnstimeofday(&now);
-		priv->hw->ptp->init_systime(priv->ioaddr, now.tv_sec,
+		ktime_get_real_ts64(&now);
+
+		/* lower 32 bits of tv_sec are safe until y2106 */
+		priv->hw->ptp->init_systime(priv->ioaddr, (u32)now.tv_sec,
 					    now.tv_nsec);
 	}