net: lan966x: Adjust maximum frame size when vlan is enabled/disabled

When vlan filtering is enabled/disabled, it is required to adjust the
maximum received frame size that it can received. When vlan filtering is
enabled, it would all to receive extra 4 bytes, that are the vlan tag.
So the maximum frame size would be 1522 with a vlan tag. If vlan
filtering is disabled then the maximum frame size would be 1518
regardless if there is or not a vlan tag.

Fixes: 6d2c186a ("net: lan966x: Add vlan support.")
Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/microchip/lan966x/lan966x_regs.h

@@ -585,6 +585,21 @@ enum lan966x_target {
 #define DEV_MAC_MAXLEN_CFG_MAX_LEN_GET(x)\
 	FIELD_GET(DEV_MAC_MAXLEN_CFG_MAX_LEN, x)
 
+/*      DEV:MAC_CFG_STATUS:MAC_TAGS_CFG */
+#define DEV_MAC_TAGS_CFG(t)       __REG(TARGET_DEV, t, 8, 28, 0, 1, 44, 12, 0, 1, 4)
+
+#define DEV_MAC_TAGS_CFG_VLAN_DBL_AWR_ENA        BIT(1)
+#define DEV_MAC_TAGS_CFG_VLAN_DBL_AWR_ENA_SET(x)\
+	FIELD_PREP(DEV_MAC_TAGS_CFG_VLAN_DBL_AWR_ENA, x)
+#define DEV_MAC_TAGS_CFG_VLAN_DBL_AWR_ENA_GET(x)\
+	FIELD_GET(DEV_MAC_TAGS_CFG_VLAN_DBL_AWR_ENA, x)
+
+#define DEV_MAC_TAGS_CFG_VLAN_AWR_ENA            BIT(0)
+#define DEV_MAC_TAGS_CFG_VLAN_AWR_ENA_SET(x)\
+	FIELD_PREP(DEV_MAC_TAGS_CFG_VLAN_AWR_ENA, x)
+#define DEV_MAC_TAGS_CFG_VLAN_AWR_ENA_GET(x)\
+	FIELD_GET(DEV_MAC_TAGS_CFG_VLAN_AWR_ENA, x)
+
 /*      DEV:MAC_CFG_STATUS:MAC_IFG_CFG */
 #define DEV_MAC_IFG_CFG(t)        __REG(TARGET_DEV, t, 8, 28, 0, 1, 44, 20, 0, 1, 4)
 

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

@@ -169,6 +169,12 @@ void lan966x_vlan_port_apply(struct lan966x_port *port)
 		ANA_VLAN_CFG_VLAN_POP_CNT,
 		lan966x, ANA_VLAN_CFG(port->chip_port));
 
+	lan_rmw(DEV_MAC_TAGS_CFG_VLAN_AWR_ENA_SET(port->vlan_aware) |
+		DEV_MAC_TAGS_CFG_VLAN_DBL_AWR_ENA_SET(port->vlan_aware),
+		DEV_MAC_TAGS_CFG_VLAN_AWR_ENA |
+		DEV_MAC_TAGS_CFG_VLAN_DBL_AWR_ENA,
+		lan966x, DEV_MAC_TAGS_CFG(port->chip_port));
+
 	/* Drop frames with multicast source address */
 	val = ANA_DROP_CFG_DROP_MC_SMAC_ENA_SET(1);
 	if (port->vlan_aware && !pvid)