[OpenWrt-Devel] [RFC] ralink: Allow to receive vlan over untag ports on MT7530

[Sven Eckelmann]

The MT7530 switch driver with enable_vlan set will automatically set all
ports to the user port mode. The hardware will remove the incoming vlan tag
on these ports and use it for its internal vlan. This is usually not wanted
and makes it impossible to communicate via vlan over the switch in both
directions.

It is possible to configure a switch port to "transparent mode" when this
port is only used as untag in the switch VLANs. This will disable the VLAN
untagging of packets when they were received on this port. The tagging on
"tag" ports based on the vlan id is still working.

The transparent port mode cannot be used when a port is both used in a VLAN
as "tag" and in another one as "untag" port.

The problem with this approach is the limit of the MTU of 1496 bytes for
the VLAN device on top of eth0.X. Larger packets can still be send but will
not be received.

Signed-off-by: Sven Eckelmann <sven at open-mesh.com>
---
 .../files/drivers/net/ethernet/ralink/mt7530.c     | 36 ++++++++++++++++++++--
 1 file changed, 33 insertions(+), 3 deletions(-)

diff --git a/target/linux/ramips/files/drivers/net/ethernet/ralink/mt7530.c b/target/linux/ramips/files/drivers/net/ethernet/ralink/mt7530.c
index 51e16f2..4e00315 100644
--- a/target/linux/ramips/files/drivers/net/ethernet/ralink/mt7530.c
+++ b/target/linux/ramips/files/drivers/net/ethernet/ralink/mt7530.c
@@ -484,6 +484,8 @@ mt7530_apply_config(struct switch_dev *dev)
 {
 	struct mt7530_priv *priv = container_of(dev, struct mt7530_priv, swdev);
 	int i, j;
+	u8 tag_ports;
+	u8 untag_ports;
 
 	if (!priv->global_vlan_enable) {
 		for (i = 0; i < MT7530_NUM_PORTS; i++)
@@ -499,9 +501,37 @@ mt7530_apply_config(struct switch_dev *dev)
 	for (i = 0; i < MT7530_NUM_PORTS; i++)
 		mt7530_w32(priv, REG_ESW_PORT_PCR(i), 0x00ff0003);
 
-	/* set all ports as user port */
-	for (i = 0; i < MT7530_NUM_PORTS; i++)
-		mt7530_w32(priv, REG_ESW_PORT_PVC(i), 0x81000000);
+	/* check if a port is used in tag/untag vlan egress mode */
+	tag_ports = 0;
+	untag_ports = 0;
+
+	for (i = 0; i < MT7530_NUM_VLANS; i++) {
+		u8 member = priv->vlan_entries[i].member;
+		u8 etags = priv->vlan_entries[i].etags;
+
+		if (!member)
+			continue;
+
+		for (j = 0; j < MT7530_NUM_PORTS; j++) {
+			if (!(member & BIT(j)))
+				continue;
+
+			if (etags & BIT(j))
+				tag_ports |= 1u << j;
+			else
+				untag_ports |= 1u << j;
+		}
+	}
+
+	/* set all untag-only ports as transparent and the rest as user port */
+	for (i = 0; i < MT7530_NUM_PORTS; i++) {
+		u32 pvc_mode = 0x81000000;
+
+		if (untag_ports & BIT(i) && !(tag_ports & BIT(i)))
+			pvc_mode = 0x810000c0;
+
+		mt7530_w32(priv, REG_ESW_PORT_PVC(i), pvc_mode);
+	}
 
 	for (i = 0; i < MT7530_NUM_VLANS; i++) {
 		u16 vid = priv->vlan_entries[i].vid;
-- 
2.5.1
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