net: dsa: mt7530: fix mirroring frames received on local port

This switch intellectual property provides a bit on the ARL global control
register which controls allowing mirroring frames which are received on the
local port (monitor port). This bit is unset after reset.

This ability must be enabled to fully support the port mirroring feature on
this switch intellectual property.

Therefore, this patch fixes the traffic not being reflected on a port,
which would be configured like below:

  tc qdisc add dev swp0 clsact

  tc filter add dev swp0 ingress matchall skip_sw \
  action mirred egress mirror dev swp0

As a side note, this configuration provides the hairpinning feature for a
single port.

Fixes: 37feab60 ("net: dsa: mt7530: add support for port mirroring")
Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/mt7530.c

@@ -2480,6 +2480,9 @@ mt7530_setup(struct dsa_switch *ds)
 			   PVC_EG_TAG(MT7530_VLAN_EG_CONSISTENT));
 	}
 
+	/* Allow mirroring frames received on the local port (monitor port). */
+	mt7530_set(priv, MT753X_AGC, LOCAL_EN);
+
 	/* Setup VLAN ID 0 for VLAN-unaware bridges */
 	ret = mt7530_setup_vlan0(priv);
 	if (ret)
@@ -2591,6 +2594,9 @@ mt7531_setup_common(struct dsa_switch *ds)
 			   PVC_EG_TAG(MT7530_VLAN_EG_CONSISTENT));
 	}
 
+	/* Allow mirroring frames received on the local port (monitor port). */
+	mt7530_set(priv, MT753X_AGC, LOCAL_EN);
+
 	/* Flush the FDB table */
 	ret = mt7530_fdb_cmd(priv, MT7530_FDB_FLUSH, NULL);
 	if (ret < 0)

drivers/net/dsa/mt7530.h

@@ -32,6 +32,10 @@ enum mt753x_id {
 #define SYSC_REG_RSTCTRL		0x34
 #define  RESET_MCM			BIT(2)
 
+/* Register for ARL global control */
+#define MT753X_AGC			0xc
+#define  LOCAL_EN			BIT(7)
+
 /* Registers to mac forward control for unknown frames */
 #define MT7530_MFC			0x10
 #define  BC_FFP(x)			(((x) & 0xff) << 24)