[PATCH] kernel: DSA roaming fix for Marvell Link Street switch series

[Tobias Waldekranz]

On Tue Feb 2, 2021 at 9:31 PM CET, DENG Qingfang wrote:
> On Tue, Feb 2, 2021 at 8:14 PM Tad <tad at spotco.us> wrote:
> >
> > I've tested this working well!
> > Devices can roam during iperf with no loss!
> > Thank you!
> >
> >
> > There are some errors in dmesg:
> > wrt1900acv1
> > mv88e6085 f1072004.mdio-mii:00: ATU member violation for [mac] portvec 20 spid 3
> >
> > wrt1200ac
> > mv88e6085 f1072004.mdio-mii:00: ATU member violation for [mac] portvec 40 spid 3
> >
> > are those expected?
>
> I think so. When your client moves back to the switch ports, the
> static entry in the ATU still points to the CPU port, so it triggers
> an ATU member violation interrupt. DSA will clear the static entry
> afterward so it is not fatal.
>
> Tobias, what happens if the switch receives a frame that violates ATU
> portvec member? Is the frame trapped to the CPU or dropped?

The frame will be dropped. So the flow will be blocked until the DSA
driver removes the static entry. Once the it has been removed, the
switch is free to learn it in the normal way again.

> Is it okay to suppress this warning?

It depends on what you mean by suppress. It is harmless in the sense
that the driver will rectify the situation ASAP, so it can safely be
_ignored_ in this scenario.

But I would strongly advise against removing the message as it often
provides important clues when debugging connectivity issues.