net: ethernet: litex: add support for 64 bit stats

Implement 64 bit per cpu stats to fix the overflow of netdev->stats
on 32 bit platforms. To simplify the code, we use net core
pcpu_sw_netstats infrastructure. One small drawback is some memory
overhead because litex uses just one queue, but we allocate the
counters per cpu.
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Acked-by: Gabriel Somlo <gsomlo@gmail.com>
Link: https://lore.kernel.org/r/20230614162035.300-1-jszhang@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/litex/litex_liteeth.c

@@ -78,8 +78,7 @@ static int liteeth_rx(struct net_device *netdev)
 	memcpy_fromio(data, priv->rx_base + rx_slot * priv->slot_size, len);
 	skb->protocol = eth_type_trans(skb, netdev);
 
-	netdev->stats.rx_packets++;
-	netdev->stats.rx_bytes += len;
+	dev_sw_netstats_rx_add(netdev, len);
 
 	return netif_rx(skb);
 
@@ -185,8 +184,7 @@ static netdev_tx_t liteeth_start_xmit(struct sk_buff *skb,
 	litex_write16(priv->base + LITEETH_READER_LENGTH, skb->len);
 	litex_write8(priv->base + LITEETH_READER_START, 1);
 
-	netdev->stats.tx_bytes += skb->len;
-	netdev->stats.tx_packets++;
+	dev_sw_netstats_tx_add(netdev, 1, skb->len);
 
 	priv->tx_slot = (priv->tx_slot + 1) % priv->num_tx_slots;
 	dev_kfree_skb_any(skb);
@@ -194,9 +192,17 @@ static netdev_tx_t liteeth_start_xmit(struct sk_buff *skb,
 	return NETDEV_TX_OK;
 }
 
+static void
+liteeth_get_stats64(struct net_device *netdev, struct rtnl_link_stats64 *stats)
+{
+	netdev_stats_to_stats64(stats, &netdev->stats);
+	dev_fetch_sw_netstats(stats, netdev->tstats);
+}
+
 static const struct net_device_ops liteeth_netdev_ops = {
 	.ndo_open		= liteeth_open,
 	.ndo_stop		= liteeth_stop,
+	.ndo_get_stats64	= liteeth_get_stats64,
 	.ndo_start_xmit         = liteeth_start_xmit,
 };
 
@@ -242,6 +248,11 @@ static int liteeth_probe(struct platform_device *pdev)
 	priv->netdev = netdev;
 	priv->dev = &pdev->dev;
 
+	netdev->tstats = devm_netdev_alloc_pcpu_stats(&pdev->dev,
+						      struct pcpu_sw_netstats);
+	if (!netdev->tstats)
+		return -ENOMEM;
+
 	irq = platform_get_irq(pdev, 0);
 	if (irq < 0)
 		return irq;