Re: [PATCH net-next v1 2/7] net: dsa: microchip: ksz8: Implement add/del_fdb and use static MAC table operations

[Oleksij Rempel <o.rempel@pengutronix.de>]

On Tue, Apr 04, 2023 at 03:50:02PM +0300, Vladimir Oltean wrote:
> On Tue, Apr 04, 2023 at 02:19:11PM +0200, Oleksij Rempel wrote:
> > If I compare KSZ879CLX and KSZ8873MLL datasheets, i do not see direct
> > answer. The only reason I can imagine is the size of static MAC table.
> > All KSZ88xx and KSZ87xx variants have only 8 entries. One is already
> > used for STP (even if STP is not enabled, can be optimized). If
> > BRIDGE_VLAN compiled, each local address will be configured 2 times.
> > So, depending on system configuration the static MAC table will full
> > very soon.
> 
> Yikes. KSZ8765 has num_statics = 8 and port_cnt = 5 (so 4 user ports I
> assume). So if all 4 user ports had their own MAC address, it would
> simply not be possible to put them under a VLAN-aware bridge, since that
> would consume 2 BR_FDB_LOCAL entries for each port, so the static MAC
> table would be full even without taking the bridge's MAC address into
> consideration.
> 
> Even with CONFIG_BRIDGE_VLAN_FILTERING turned off or with the bridge
> option vlan_default_pvid = 0, this would still consume 4 BR_FDB_LOCAL
> entries + one for the bridge's MAC address + 1 for STP, leaving only 2
> entries usable for *both* bridge fdb, *and* bridge mdb.
> 
> I haven't opened the datasheets of these chips. Is it possible to use
> the dynamic MAC table to store static(-ish) entries?

According to KSZ8795CLX datasheet, dynamic MAC table is read-only.
But there is Access Control Lists (ACL) with 16 entries. It is possible
created a forwarding rule with match against DST MAC address.

Beside, I'm working right now on KSZ9477 tc-flower support based on ACL
implementation.

Regards,
Oleksij
-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |