mlxsw: spectrum_switchdev: Add support for maintaining list of ports per MDB entry

mlxsw: spectrum_switchdev: Add support for maintaining list of ports per MDB entry

As part of converting MDB code to use PGT APIs, PGT code stores which ports
are mapped to each PGT entry. PGT code is not aware of the type of the port
(multicast router or not), as it is not relevant there.

To be able to release an MDB entry when the there are no ports which are
not multicast routers, the entry should be aware of the state of its
ports. Add support for maintaining list of ports per MDB entry.

Each port will hold a reference count as multiple MDB entries can use the
same hardware MDB entry. It occurs because MDB entries in the Linux bridge
are keyed according to their multicast IP, when these entries are notified
to device drivers via switchdev, the multicast IP is converted to a
multicast MAC. This conversion might cause collisions, for example,
ff0e::1 and ff0e:1234::1 are both mapped to the multicast MAC
33:33:00:00:00:01.

Multicast router port will take a reference once, and will be marked as
'mrouter', then when port in the list is multicast router and its
reference value is one, it means that the entry can be removed in case
that there are no other ports which are not multicast routers. For that,
maintain a counter per MDB entry to count ports in the list, which were
added to the multicast group, and not because they are multicast routers.
When this counter is zero, the entry can be removed.

Add mlxsw_sp_mdb_entry_port_{get,put}() for regular ports and
mlxsw_sp_mdb_entry_mrouter_port_{get,put}() for multicast router ports.
Call PGT API to add or remove port from PGT entry when port is first added
or removed, according to the reference counting.

Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>