[PATCH net v4 4/7] net: dsa: mt7530: fix handling of BPDUs on MT7530 switch

[arinc9 . unal]

From: Arınç ÜNAL <arinc.unal@xxxxxxxxxx>

BPDUs are link-local frames, therefore they must be trapped to the CPU
port. Currently, the MT7530 switch treats BPDUs as regular multicast
frames, therefore flooding them to user ports. To fix this, set BPDUs to be
trapped to the CPU port.

BPDUs received from a user port will be trapped to the numerically smallest
CPU port which is affine to the DSA conduit interface that is up.

Fixes: b8f126a8d543 ("net-next: dsa: add dsa support for Mediatek MT7530 switch")
Signed-off-by: Arınç ÜNAL <arinc.unal@xxxxxxxxxx>
---
 drivers/net/dsa/mt7530.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c
index 2bde2fdb5fba..e4c169843f2e 100644
--- a/drivers/net/dsa/mt7530.c
+++ b/drivers/net/dsa/mt7530.c
@@ -2259,6 +2259,10 @@ mt7530_setup(struct dsa_switch *ds)
 
 	priv->p6_interface = PHY_INTERFACE_MODE_NA;
 
+	/* Trap BPDUs to the CPU port */
+	mt7530_rmw(priv, MT753X_BPC, MT753X_BPDU_PORT_FW_MASK,
+		   MT753X_BPDU_CPU_ONLY);
+
 	/* Enable and reset MIB counters */
 	mt7530_mib_reset(ds);
 
-- 
2.39.2