[PATCH net] net: dsa: motorcomm: Do not inherit ports from dynamic FDB entries

[David Yang <mmyangfl@gmail.com>]

When adding an fdb/mdb entry that the hardware has already learned as
dynamic, the learned ports were silently converted into the static
entry, which DSA loses track of; the entry is silently expanded and can
never be deleted. Replace the port mask instead of merging when the
existing entry is not static.

Found by code inspection.

Fixes: 186623f4aa72 ("net: dsa: yt921x: Add support for Motorcomm YT921x")
Signed-off-by: David Yang <mmyangfl@gmail.com>
---
 drivers/net/dsa/motorcomm/chip.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/dsa/motorcomm/chip.c b/drivers/net/dsa/motorcomm/chip.c
index a7a9a7439304..6efd74e7eac6 100644
--- a/drivers/net/dsa/motorcomm/chip.c
+++ b/drivers/net/dsa/motorcomm/chip.c
@@ -805,7 +805,10 @@ yt921x_fdb_join(struct yt921x_priv *priv, const unsigned char *addr, u16 vid,
 
 	ctrl1 = val1 & ~YT921X_FDB_IO1_STATUS_M;
 	ctrl1 |= YT921X_FDB_IO1_STATUS_STATIC;
-	ctrl2 = val2 | YT921X_FDB_IO2_EGR_PORTS(ports_mask);
+	ctrl2 = val2;
+	if (ctrl1 != val1)
+		ctrl2 &= ~YT921X_FDB_IO2_EGR_PORTS_M;
+	ctrl2 |= YT921X_FDB_IO2_EGR_PORTS(ports_mask);
 	if (ctrl1 == val1 && ctrl2 == val2)
 		return 0;
 
-- 
2.53.0