Hello Siddharth

On 05/02/26 13:45, Siddharth Vadapalli wrote:

On Thu, 2026-02-05 at 12:39 +0530, Chintan Vankar wrote:

quoted

Multicast entry rules are mainly evaluated for receiving traffic and do not
require MAC ports to be explicitly associated with them. However, setting
associated MAC port's bit to the port_mask of the ALE entry ensures
technical correctness and helps maintaining ALE entries linked to MAC
ports.

Signed-off-by: Chintan Vankar <redacted>
---
  drivers/net/ethernet/ti/am65-cpsw-nuss.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/ti/am65-cpsw-nuss.c b/drivers/net/ethernet/ti/am65-cpsw-nuss.c
index 5924db6be3fe..967918050433 100644
--- a/drivers/net/ethernet/ti/am65-cpsw-nuss.c
+++ b/drivers/net/ethernet/ti/am65-cpsw-nuss.c

@@ -391,7 +391,7 @@ static void am65_cpsw_nuss_ndo_slave_set_rx_mode(struct net_device *ndev)
  	cpsw_ale_set_allmulti(common->ale,
  			      ndev->flags & IFF_ALLMULTI, port->port_id);
  
-	port_mask = ALE_PORT_HOST;
+	port_mask = BIT(port->port_id) | ALE_PORT_HOST;

Since the port_mask setup above is passed to 'cpsw_ale_flush_multicast()'
below, wouldn't it temporarily cause the forwarded multicast traffic to be
dropped?

quoted

  	/* Clear all mcast from ALE */
  	cpsw_ale_flush_multicast(common->ale, port_mask, -1);

The code in the driver following the above function call is:

	if (!netdev_mc_empty(ndev)) {
		struct netdev_hw_addr *ha;

		/* program multicast address list into ALE register */
		netdev_for_each_mc_addr(ha, ndev) {
			cpsw_ale_add_mcast(common->ale, ha->addr,
					   port_mask, 0, 0, 0);
		}
	}

So we do add back the multicast entries for the same 'port_mask' that we
removed earlier during cpsw_ale_flush_multicast(), but, there is a delay
between flushing the entries in cpsw_ale_flush_multicast() and adding them
back via cpsw_ale_add_mcast(). During that period, the multicast traffic on
the forwarding path between MAC Ports will be momentarily dropped. Please
clarify if that isn't the case.

When "cpsw_ale_flush_multicast()" is called, it only deletes entries
where the resulting port_mask becomes "0x0" or "ALE_PORT_HOST" (as per
the function implementation "cpsw_ale_flush_multicast()" in cpsw_ale.c).

For multicast entries shared across multiple ports, the function only
clears the specific port's bit from the port_mask without deleting the
entry itself. This prevents any traffic disruption for other active
ports.

Regards,
Chintan.

Regards,
Siddharth.