On Mon, Mar 29, 2021 at 12:04:39AM +0200, Andrew Lunn wrote:

On Mon, Mar 29, 2021 at 12:53:09AM +0300, Vladimir Oltean wrote:

quoted

On Sun, Mar 28, 2021 at 05:52:43PM +0200, Andrew Lunn wrote:

quoted

quoted

+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.

I agree, and this is a particular feature of Marvell, not something that
can be said in general. However, I have nothing against deleting the
dsa_is_dsa_port checks from dsa_switch_tag_proto_match and from Tobias'
patch, since nobody needs them at the moment.