Re: [PATCH net-next 2/3] net: dsa: Allow default tag protocol to be overridden from DT

Andrew Lunn
2021-03-28T22:05:50Z

On Mon, Mar 29, 2021 at 12:53:09AM +0300, Vladimir Oltean wrote:
> On Sun, Mar 28, 2021 at 05:52:43PM +0200, Andrew Lunn wrote:
> > > +static int dsa_switch_setup_tag_protocol(struct dsa_switch *ds)
> > > +{
> > > + const struct dsa_device_ops *tag_ops = ds->dst->tag_ops;
> > > + struct dsa_switch_tree *dst = ds->dst;
> > > + int port, err;
> > > +
> > > + if (tag_ops->proto == dst->default_proto)
> > > + return 0;
> > > +
> > > + if (!ds->ops->change_tag_protocol) {
> > > + dev_err(ds->dev, "Tag protocol cannot be modified\n");
> > > + return -EINVAL;
> > > + }
> > > +
> > > + for (port = 0; port < ds->num_ports; port++) {
> > > + if (!(dsa_is_dsa_port(ds, port) || dsa_is_cpu_port(ds, port)))
> > > + continue;
> >
> > dsa_is_dsa_port() is interesting. Do we care about the tagging
> > protocol on DSA ports? We never see that traffic?
>
> I believe this comes from me (see dsa_switch_tag_proto_match). I did not
> take into consideration at that time the fact that Marvell switches can
> translate between DSA and EDSA. So I assumed that every switch in the
> tree needs a notification about the tagging protocol, not just the
> top-most one.

Hi Vladimir

static int mv88e6xxx_setup_port_mode(struct mv88e6xxx_chip *chip, int port)
{
if (dsa_is_dsa_port(chip->ds, port))
return mv88e6xxx_set_port_mode_dsa(chip, port);

So DSA ports, the ports connecting two switches together, are hard
coded to use DSA.

if (dsa_is_user_port(chip->ds, port))
return mv88e6xxx_set_port_mode_normal(chip, port);

/* Setup CPU port mode depending on its supported tag format */
if (chip->info->tag_protocol == DSA_TAG_PROTO_DSA)
return mv88e6xxx_set_port_mode_dsa(chip, port);

if (chip->info->tag_protocol == DSA_TAG_PROTO_EDSA)
return mv88e6xxx_set_port_mode_edsa(chip, port);

CPU ports can be configured to DSA or EDSA.

The switches seem happy to translate between DSA and EDSA as needed.

Andrew