[PATCH net v4 5/7] net: stmmac: Disable S-Tag processing on dwmac4

[Ovidiu Panait]

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 S-Tag stripping correctly. Therefore, restrict the
NETIF_F_HW_VLAN_STAG_RX and NETIF_F_HW_VLAN_STAG_FILTER advertisement
to dwxgmac2 only.

With this, 802.1ad tags are left in place and handled by the software
VLAN path.

Fixes: 750011e239a5 ("net: stmmac: Add support for HW-accelerated VLAN stripping")
Signed-off-by: Ovidiu Panait <ovidiu.panait.rb at renesas.com>
---
v4 changes:
- Dropped all "double VLAN" references from the commit title/message.
- Rebased on top of the S-VLAN rework.

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 | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index c81c5bb5b075..eab2903a66e4 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -7952,15 +7952,20 @@ 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;
-	priv->hw->hw_svlan_en = true;
+	ndev->features |= NETIF_F_HW_VLAN_CTAG_RX;
+	if (priv->plat->core_type == DWMAC_CORE_XGMAC) {
+		ndev->features |= NETIF_F_HW_VLAN_STAG_RX;
+		priv->hw->hw_svlan_en = true;
+	}
+
 	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;
-- 
2.34.1