net: lan966x: Make sure to insert the vlan tags also in host mode

[ Upstream commit 27eab4c ]

When running these commands on DUT (and similar at the other end)
ip link set dev eth0 up
ip link add link eth0 name eth0.10 type vlan id 10
ip addr add 10.0.0.1/24 dev eth0.10
ip link set dev eth0.10 up
ping 10.0.0.2

The ping will fail.

The reason why is failing is because, the network interfaces for lan966x
have a flag saying that the HW can insert the vlan tags into the
frames(NETIF_F_HW_VLAN_CTAG_TX). Meaning that the frames that are
transmitted don't have the vlan tag inside the skb data, but they have
it inside the skb. We already get that vlan tag and put it in the IFH
but the problem is that we don't configure the HW to rewrite the frame
when the interface is in host mode.
The fix consists in actually configuring the HW to insert the vlan tag
if it is different than 0.

Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Fixes: 6d2c186 ("net: lan966x: Add vlan support.")
Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Link: https://patch.msgid.link/20250528093619.3738998-1-horatiu.vultur@microchip.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: HoratiuVultur

drivers/net/ethernet/microchip/lan966x/lan966x_main.c

@@ -880,6 +880,7 @@ static int lan966x_probe_port(struct lan966x *lan966x, u32 p,
 	lan966x_vlan_port_set_vlan_aware(port, 0);
 	lan966x_vlan_port_set_vid(port, HOST_PVID, false, false);
 	lan966x_vlan_port_apply(port);
+	lan966x_vlan_port_rew_host(port);
 
 	return 0;
 }

drivers/net/ethernet/microchip/lan966x/lan966x_main.h

@@ -497,6 +497,7 @@ void lan966x_vlan_port_apply(struct lan966x_port *port);
 bool lan966x_vlan_cpu_member_cpu_vlan_mask(struct lan966x *lan966x, u16 vid);
 void lan966x_vlan_port_set_vlan_aware(struct lan966x_port *port,
 				      bool vlan_aware);
+void lan966x_vlan_port_rew_host(struct lan966x_port *port);
 int lan966x_vlan_port_set_vid(struct lan966x_port *port,
 			      u16 vid,
 			      bool pvid,

drivers/net/ethernet/microchip/lan966x/lan966x_switchdev.c

@@ -297,6 +297,7 @@ static void lan966x_port_bridge_leave(struct lan966x_port *port,
 	lan966x_vlan_port_set_vlan_aware(port, false);
 	lan966x_vlan_port_set_vid(port, HOST_PVID, false, false);
 	lan966x_vlan_port_apply(port);
+	lan966x_vlan_port_rew_host(port);
 }
 
 int lan966x_port_changeupper(struct net_device *dev,

drivers/net/ethernet/microchip/lan966x/lan966x_vlan.c

@@ -149,6 +149,27 @@ void lan966x_vlan_port_set_vlan_aware(struct lan966x_port *port,
 	port->vlan_aware = vlan_aware;
 }
 
+/* When the interface is in host mode, the interface should not be vlan aware
+ * but it should insert all the tags that it gets from the network stack.
+ * The tags are not in the data of the frame but actually in the skb and the ifh
+ * is configured already to get this tag. So what we need to do is to update the
+ * rewriter to insert the vlan tag for all frames which have a vlan tag
+ * different than 0.
+ */
+void lan966x_vlan_port_rew_host(struct lan966x_port *port)
+{
+	struct lan966x *lan966x = port->lan966x;
+	u32 val;
+
+	/* Tag all frames except when VID=0*/
+	val = REW_TAG_CFG_TAG_CFG_SET(2);
+
+	/* Update only some bits in the register */
+	lan_rmw(val,
+		REW_TAG_CFG_TAG_CFG,
+		lan966x, REW_TAG_CFG(port->chip_port));
+}
+
 void lan966x_vlan_port_apply(struct lan966x_port *port)
 {
 	struct lan966x *lan966x = port->lan966x;