[PATCH net v3 3/5] net: stmmac: Disable double VLAN handling on dwmac4

Currently, hardware VLAN stripping is broken for 802.1ad tags. vlan_rx_hw()
hardcodes ETH_P_8021Q when putting the hardware tag into the skb, rather
than using the actual protocol from the packet. Because of this, packets
that contain a 802.1ad outer tag are incorrectly passed up the stack as
having an 802.1Q tag. This causes QinQ ping between two hosts to fail.

vlan_rx_hw() is shared by dwxgmac2 and dwmac4: on dwxgmac2 the tag type
is available in the RDES3 write-back descriptor (the ET_LT field), so the
outer tag type can be determined based on that info. However, dwmac4
doesn't seem to provide the tag type. The Length/Type field in RDES3 only
indicates whether the packet is single or double-tagged, not which tag
type was stripped.

Since dwmac4 cannot report the stripped tag type, it cannot support
hardware double VLAN stripping correctly. Disable it by dropping
update_dvlan_state from dwmac_vlan_ops. With this, 802.1ad tags are
left in place and handled by the software VLAN path.

Also, restrict the NETIF_F_HW_VLAN_STAG_RX and NETIF_F_HW_VLAN_STAG_FILTER
advertisement to dwxgmac2.

Fixes: 750011e239a5 ("net: stmmac: Add support for HW-accelerated VLAN stripping")
Signed-off-by: Ovidiu Panait <redacted>
---
v3 changes:
- Rebased after dropping the dma_cap.dvlan patch.

v2 changes:
- Advertised NETIF_F_HW_VLAN_STAG_RX and NETIF_F_HW_VLAN_STAG_FILTER only
  for XGMAC (reported by Sashiko).

 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 8 ++++++--
 drivers/net/ethernet/stmicro/stmmac/stmmac_vlan.c | 1 -
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index e79b37fc716c..7b6a506ce4c1 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -7956,14 +7956,18 @@ static int __stmmac_dvr_probe(struct device *device,
 	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;
+	ndev->features |= NETIF_F_HW_VLAN_CTAG_RX;
+	if (priv->plat->core_type == DWMAC_CORE_XGMAC)
+		ndev->features |= NETIF_F_HW_VLAN_STAG_RX;
+
 	if (dwmac_is_xmac(priv->plat->core_type)) {
 		ndev->hw_features |= NETIF_F_HW_VLAN_CTAG_RX;
 		priv->hw->hw_vlan_en = true;
 	}
 	if (priv->dma_cap.vlhash) {
 		ndev->features |= NETIF_F_HW_VLAN_CTAG_FILTER;
-		ndev->features |= NETIF_F_HW_VLAN_STAG_FILTER;
+		if (priv->plat->core_type == DWMAC_CORE_XGMAC)
+			ndev->features |= NETIF_F_HW_VLAN_STAG_FILTER;
 	}
 	if (priv->dma_cap.vlins)
 		ndev->features |= NETIF_F_HW_VLAN_CTAG_TX;

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_vlan.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_vlan.c
index 1e47ae62093e..9b5b3f11f699 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_vlan.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_vlan.c

@@ -273,7 +273,6 @@ static void dwxgmac2_update_vlan_hash(struct mac_device_info *hw, u32 hash)
 
 const struct stmmac_vlan_ops dwmac_vlan_ops = {
 	.update_vlan_hash = vlan_update_hash,
-	.update_dvlan_state = vlan_update_dvlan_state,
 	.enable_vlan = vlan_enable,
 	.add_hw_vlan_rx_fltr = vlan_add_hw_rx_fltr,
 	.del_hw_vlan_rx_fltr = vlan_del_hw_rx_fltr,

-- 
2.34.1