[PATCH net v8 2/2] net: stmmac: remove software VLAN tag stripping

[peilinhe2020@163.com]

From: Peilin He <he.peilin@zte.com.cn>

The software VLAN stripping logic in stmmac_rx_vlan() was originally
introduced in 2014 by commit b93819854d6e ("stmmac: Add vlan rx for
better GRO performance.") as a workaround to improve GRO performance,
since at that time GRO could not handle frames with VLAN tags. However,
this limitation was resolved in 2015 by commit 66e5133f19e9 ("vlan: Add
GRO support for non hardware accelerated vlan"), which added GRO support
for non-hardware-accelerated VLAN frames. Keeping a software fallback
path for VLAN stripping is no longer necessary and only adds complexity.

After removing it, VLAN tags remain in the packet. Adjust
stmmac_has_ip_ethertype() to tolerate a single in-payload VLAN tag so
that the MAC RX checksum offload result is still used for tagged
IPv4/IPv6 frames on cores without MAC-level stripping.

This intentionally changes the advertised features:
- dwmac100/dwmac1000 no longer advertise NETIF_F_HW_VLAN_CTAG_RX;
  they have no hardware VLAN stripping.
- NETIF_F_HW_VLAN_STAG_RX is no longer advertised, as the hardware
  reports stripped S-tags as C-tags.
- On xmac cores NETIF_F_HW_VLAN_CTAG_RX is advertised only when the
  VLAN ops provide .set_hw_vlan_mode and .rx_hw_vlan, so DWXLGMAC no
  longer falsely advertises RX VLAN offload.

With NETIF_F_VLAN_FEATURES possibly empty, EEE RX clock stop may be
enabled on some platforms; the preceding selftests patch blocks RX
clock stop while the ethtool selftests run.

This depends on the preceding selftests fix.

Suggested-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Signed-off-by: Peilin He <he.peilin@zte.com.cn>
Reviewed-by: xu xin <xu.xin16@zte.com.cn>
Reviewed-by: Jiang Kun <jiang.kun2@zte.com.cn>
---
 .../net/ethernet/stmicro/stmmac/stmmac_main.c | 38 +++++--------------
 1 file changed, 10 insertions(+), 28 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 9c9e95d66b09..6d4716b1a7ad 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -4752,7 +4752,11 @@ static bool stmmac_has_ip_ethertype(struct sk_buff *skb)
 	proto = __vlan_get_protocol(skb, eth_header_parse_protocol(skb),
 				    &depth);
 
-	return (depth <= ETH_HLEN) &&
+	/* Software VLAN stripping is gone, so a single VLAN tag may
+	 * still be present. The MAC RX checksum result still applies
+	 * to the inner IP packet.
+	 */
+	return (depth <= VLAN_ETH_HLEN) &&
 		(proto == htons(ETH_P_IP) || proto == htons(ETH_P_IPV6));
 }
 
@@ -5032,24 +5036,6 @@ static netdev_features_t stmmac_features_check(struct sk_buff *skb,
 	return vlan_features_check(skb, features);
 }
 
-static void stmmac_rx_vlan(struct net_device *dev, struct sk_buff *skb)
-{
-	struct vlan_ethhdr *veth = skb_vlan_eth_hdr(skb);
-	__be16 vlan_proto = veth->h_vlan_proto;
-	u16 vlanid;
-
-	if ((vlan_proto == htons(ETH_P_8021Q) &&
-	     dev->features & NETIF_F_HW_VLAN_CTAG_RX) ||
-	    (vlan_proto == htons(ETH_P_8021AD) &&
-	     dev->features & NETIF_F_HW_VLAN_STAG_RX)) {
-		/* pop the vlan tag */
-		vlanid = ntohs(veth->h_vlan_TCI);
-		memmove(skb->data + VLAN_HLEN, veth, ETH_ALEN * 2);
-		skb_pull(skb, VLAN_HLEN);
-		__vlan_hwaccel_put_tag(skb, vlan_proto, vlanid);
-	}
-}
-
 /**
  * stmmac_rx_refill - refill used skb preallocated buffers
  * @priv: driver private structure
@@ -5418,9 +5404,7 @@ static void stmmac_dispatch_skb_zc(struct stmmac_priv *priv, u32 queue,
 	if (priv->hw->hw_vlan_en)
 		/* MAC level stripping. */
 		stmmac_rx_hw_vlan(priv, priv->hw, p, skb);
-	else
-		/* Driver level stripping. */
-		stmmac_rx_vlan(priv->dev, skb);
+
 	skb->protocol = eth_type_trans(skb, priv->dev);
 
 	if (unlikely(!coe) || !stmmac_has_ip_ethertype(skb))
@@ -5912,9 +5896,6 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit, u32 queue)
 		if (priv->hw->hw_vlan_en)
 			/* MAC level stripping. */
 			stmmac_rx_hw_vlan(priv, priv->hw, p, skb);
-		else
-			/* Driver level stripping. */
-			stmmac_rx_vlan(priv->dev, skb);
 
 		skb->protocol = eth_type_trans(skb, priv->dev);
 
@@ -7995,9 +7976,10 @@ static int __stmmac_dvr_probe(struct device *device,
 	ndev->features |= ndev->hw_features | NETIF_F_HIGHDMA;
 	ndev->watchdog_timeo = msecs_to_jiffies(watchdog);
 #ifdef STMMAC_VLAN_TAG_USED
-	/* Both mac100 and gmac support receive VLAN tag detection */
-	ndev->features |= NETIF_F_HW_VLAN_CTAG_RX | NETIF_F_HW_VLAN_STAG_RX;
-	if (dwmac_is_xmac(priv->plat->core_type)) {
+	if (priv->hw->vlan &&
+	    priv->hw->vlan->set_hw_vlan_mode &&
+	    priv->hw->vlan->rx_hw_vlan) {
+		ndev->features |= NETIF_F_HW_VLAN_CTAG_RX;
 		ndev->hw_features |= NETIF_F_HW_VLAN_CTAG_RX;
 		priv->hw->hw_vlan_en = true;
 	}
-- 
2.43.0