net: axienet: Switch to 64-bit RX/TX statistics

The RX and TX byte/packet statistics in this driver could be overflowed
relatively quickly on a 32-bit platform. Switch these stats to use the
u64_stats infrastructure to avoid this.

Signed-off-by: Robert Hancock <robert.hancock@calian.com>
Link: https://lore.kernel.org/r/20220829233901.3429419-1-robert.hancock@calian.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/xilinx/xilinx_axienet.h

@@ -402,6 +402,9 @@ struct axidma_bd {
  * @rx_bd_num:	Size of RX buffer descriptor ring
  * @rx_bd_ci:	Stores the index of the Rx buffer descriptor in the ring being
  *		accessed currently.
+ * @rx_packets: RX packet count for statistics
+ * @rx_bytes:	RX byte count for statistics
+ * @rx_stat_sync: Synchronization object for RX stats
  * @napi_tx:	NAPI TX control structure
  * @tx_dma_cr:  Nominal content of TX DMA control register
  * @tx_bd_v:	Virtual address of the TX buffer descriptor ring
@@ -411,6 +414,9 @@ struct axidma_bd {
  *		complete. Only updated at runtime by TX NAPI poll.
  * @tx_bd_tail:	Stores the index of the next Tx buffer descriptor in the ring
  *              to be populated.
+ * @tx_packets: TX packet count for statistics
+ * @tx_bytes:	TX byte count for statistics
+ * @tx_stat_sync: Synchronization object for TX stats
  * @dma_err_task: Work structure to process Axi DMA errors
  * @tx_irq:	Axidma TX IRQ number
  * @rx_irq:	Axidma RX IRQ number
@@ -458,6 +464,9 @@ struct axienet_local {
 	dma_addr_t rx_bd_p;
 	u32 rx_bd_num;
 	u32 rx_bd_ci;
+	u64_stats_t rx_packets;
+	u64_stats_t rx_bytes;
+	struct u64_stats_sync rx_stat_sync;
 
 	struct napi_struct napi_tx;
 	u32 tx_dma_cr;
@@ -466,6 +475,9 @@ struct axienet_local {
 	u32 tx_bd_num;
 	u32 tx_bd_ci;
 	u32 tx_bd_tail;
+	u64_stats_t tx_packets;
+	u64_stats_t tx_bytes;
+	struct u64_stats_sync tx_stat_sync;
 
 	struct work_struct dma_err_task;
 

drivers/net/ethernet/xilinx/xilinx_axienet_main.c

@@ -752,8 +752,10 @@ static int axienet_tx_poll(struct napi_struct *napi, int budget)
 		if (lp->tx_bd_ci >= lp->tx_bd_num)
 			lp->tx_bd_ci %= lp->tx_bd_num;
 
-		ndev->stats.tx_packets += packets;
-		ndev->stats.tx_bytes += size;
+		u64_stats_update_begin(&lp->tx_stat_sync);
+		u64_stats_add(&lp->tx_packets, packets);
+		u64_stats_add(&lp->tx_bytes, size);
+		u64_stats_update_end(&lp->tx_stat_sync);
 
 		/* Matches barrier in axienet_start_xmit */
 		smp_mb();
@@ -984,8 +986,10 @@ static int axienet_rx_poll(struct napi_struct *napi, int budget)
 		cur_p = &lp->rx_bd_v[lp->rx_bd_ci];
 	}
 
-	lp->ndev->stats.rx_packets += packets;
-	lp->ndev->stats.rx_bytes += size;
+	u64_stats_update_begin(&lp->rx_stat_sync);
+	u64_stats_add(&lp->rx_packets, packets);
+	u64_stats_add(&lp->rx_bytes, size);
+	u64_stats_update_end(&lp->rx_stat_sync);
 
 	if (tail_p)
 		axienet_dma_out_addr(lp, XAXIDMA_RX_TDESC_OFFSET, tail_p);
@@ -1292,10 +1296,32 @@ static int axienet_ioctl(struct net_device *dev, struct ifreq *rq, int cmd)
 	return phylink_mii_ioctl(lp->phylink, rq, cmd);
 }
 
+static void
+axienet_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats)
+{
+	struct axienet_local *lp = netdev_priv(dev);
+	unsigned int start;
+
+	netdev_stats_to_stats64(stats, &dev->stats);
+
+	do {
+		start = u64_stats_fetch_begin_irq(&lp->rx_stat_sync);
+		stats->rx_packets = u64_stats_read(&lp->rx_packets);
+		stats->rx_bytes = u64_stats_read(&lp->rx_bytes);
+	} while (u64_stats_fetch_retry_irq(&lp->rx_stat_sync, start));
+
+	do {
+		start = u64_stats_fetch_begin_irq(&lp->tx_stat_sync);
+		stats->tx_packets = u64_stats_read(&lp->tx_packets);
+		stats->tx_bytes = u64_stats_read(&lp->tx_bytes);
+	} while (u64_stats_fetch_retry_irq(&lp->tx_stat_sync, start));
+}
+
 static const struct net_device_ops axienet_netdev_ops = {
 	.ndo_open = axienet_open,
 	.ndo_stop = axienet_stop,
 	.ndo_start_xmit = axienet_start_xmit,
+	.ndo_get_stats64 = axienet_get_stats64,
 	.ndo_change_mtu	= axienet_change_mtu,
 	.ndo_set_mac_address = netdev_set_mac_address,
 	.ndo_validate_addr = eth_validate_addr,
@@ -1850,6 +1876,9 @@ static int axienet_probe(struct platform_device *pdev)
 	lp->rx_bd_num = RX_BD_NUM_DEFAULT;
 	lp->tx_bd_num = TX_BD_NUM_DEFAULT;
 
+	u64_stats_init(&lp->rx_stat_sync);
+	u64_stats_init(&lp->tx_stat_sync);
+
 	netif_napi_add(ndev, &lp->napi_rx, axienet_rx_poll, NAPI_POLL_WEIGHT);
 	netif_napi_add(ndev, &lp->napi_tx, axienet_tx_poll, NAPI_POLL_WEIGHT);