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

[Tobias Waldekranz]

On Tue Feb 2, 2021 at 11:03 PM CET, DENG Qingfang wrote:
> On Tue, Feb 2, 2021 at 9:22 PM Tobias Waldekranz <tobias at waldekranz.com>
> wrote:
> >
> > >
> > > 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.
>
> Can the switch be configured to trap those frames to the CPU? So the
> bridge subsystem can handle them.

AFAIK, no. There is a per-port bit that you can set to ignore the
errors, i.e. no violation is generated, but I am pretty sure that the
frame is still dropped.

This is why you really want the CPU to send FORWARDs. That way, the
switch can handle all aging entries. It is on my TODO, but it is not
obvious how to get the bridge to cooperate.

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

Today it uses dev_err_ratelimited, which seems sensible to me. My
guess is 99% of users won't have debug messages compiled in, so that
is essentially the same as removing it.