[PATCH] mt7530 fix mt7530_fdb_write vid missing ivl bit

[DENG Qingfang]

On Fri, Jul 16, 2021 at 05:22:11PM +0200, ericwouds at gmail.com wrote:
> From: Eric Woudstra <37153012+ericwoud at users.noreply.github.com>
> 
> According to reference guides mt7530 (mt7620) and mt7531:
> 
> NOTE: When IVL is reset, MAC[47:0] and FID[2:0] will be used to 
> read/write the address table. When IVL is set, MAC[47:0] and CVID[11:0] 
> will be used to read/write the address table.
> 
> Since the function only fills in CVID and no FID, we need to set the
> IVL bit. The existing code does not set it.
> 
> This is a fix for the issue I dropped here earlier:
> 
> http://lists.infradead.org/pipermail/linux-mediatek/2021-June/025697.html
> 
> With this patch, it is now possible to delete the 'self' fdb entry
> manually. However, wifi roaming still has the same issue, the entry
> does not get deleted automatically. Wifi roaming also needs a fix
> somewhere else to function correctly in combination with vlan.

Sorry to bump this up, but I think I identified the issue:

Consider a VLAN-aware bridge br0, with two ports set to different PVIDs:

> bridge vlan
> port         vlan-id
> swp0         1 PVID Egress Untagged
> swp1         2 PVID Egress Untagged

When the bridge core sends a packet to swp1, the packet will be sent to
the CPU port of the switch as untagged because swp1 is set as "Egress
Untagged". However if the switch uses independent VLAN learning, the CPU
port PVID will be used to update the FDB. As we don't change its PVID
(not reasonable to change it anyway), hardware learning may not update
the correct FDB.

A possible solution is always send packets as tagged when serving a
VLAN-aware bridge.

mv88e6xxx has been using hardware learning on CPU port since commit
d82f8ab0d874 ("net: dsa: tag_dsa: offload the bridge forwarding process"),
does it have the same issue?