On Thu, Apr 15, 2021 at 11:26:09AM +0200, Tobias Waldekranz wrote: > Some combinations of tag protocols and Ethernet controllers are > incompatible, and it is hard for the driver to keep track of these. > > Therefore, allow the device tree author (typically the board vendor) > to inform the driver of this fact by selecting an alternate protocol > that is known to work. > > Signed-off-by: Tobias Waldekranz <tob...@waldekranz.com> > --- > include/net/dsa.h | 5 +++ > net/dsa/dsa2.c | 95 ++++++++++++++++++++++++++++++++++++++--------- > 2 files changed, 83 insertions(+), 17 deletions(-) > > diff --git a/include/net/dsa.h b/include/net/dsa.h > index 1259b0f40684..2b25fe1ad5b7 100644 > --- a/include/net/dsa.h > +++ b/include/net/dsa.h > @@ -149,6 +149,11 @@ struct dsa_switch_tree { > /* Tagging protocol operations */ > const struct dsa_device_ops *tag_ops; > > + /* Default tagging protocol preferred by the switches in this > + * tree. > + */ > + enum dsa_tag_protocol default_proto; > + > /* > * Configuration data for the platform device that owns > * this dsa switch tree instance. > diff --git a/net/dsa/dsa2.c b/net/dsa/dsa2.c > index d7c22e3a1fbf..80dbf8b6bf8f 100644 > --- a/net/dsa/dsa2.c > +++ b/net/dsa/dsa2.c > @@ -668,6 +668,35 @@ static const struct devlink_ops dsa_devlink_ops = { > .sb_occ_tc_port_bind_get = dsa_devlink_sb_occ_tc_port_bind_get, > }; > > +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; > + }
We validated this already here: if (ds->ops->change_tag_protocol) { tag_ops = dsa_find_tagger_by_name(user_protocol); } else { dev_err(ds->dev, "Tag protocol cannot be modified\n"); return -EINVAL; } > + > + for (port = 0; port < ds->num_ports; port++) { > + if (!dsa_is_cpu_port(ds, port)) > + continue; > + > + err = ds->ops->change_tag_protocol(ds, port, tag_ops->proto); > + if (err) { > + dev_err(ds->dev, "Tag protocol \"%s\" is not > supported\n", > + tag_ops->name); Maybe instead of saying "is not supported", you can say "Changing the tag protocol to \"%s\" returned %pe", tag_ops->name, ERR_PTR(err) which is a bit more informative. > + return err; > + } > + } > + > + return 0; > +} > + > static int dsa_switch_setup(struct dsa_switch *ds) > { > struct dsa_devlink_priv *dl_priv; > @@ -718,6 +747,10 @@ static int dsa_switch_setup(struct dsa_switch *ds) > if (err < 0) > goto unregister_notifier; > > + err = dsa_switch_setup_tag_protocol(ds); > + if (err) > + goto teardown; > + > devlink_params_publish(ds->devlink); > > if (!ds->slave_mii_bus && ds->ops->phy_read) { > @@ -1068,34 +1101,60 @@ static enum dsa_tag_protocol > dsa_get_tag_protocol(struct dsa_port *dp, > return ds->ops->get_tag_protocol(ds, dp->index, tag_protocol); > } > > -static int dsa_port_parse_cpu(struct dsa_port *dp, struct net_device *master) > +static int dsa_port_parse_cpu(struct dsa_port *dp, struct net_device *master, > + const char *user_protocol) > { > struct dsa_switch *ds = dp->ds; > struct dsa_switch_tree *dst = ds->dst; > const struct dsa_device_ops *tag_ops; > - enum dsa_tag_protocol tag_protocol; > + enum dsa_tag_protocol default_proto; > + > + /* Find out which protocol the switch would prefer. */ > + default_proto = dsa_get_tag_protocol(dp, master); > + if (dst->default_proto) { > + if (dst->default_proto != default_proto) { > + dev_err(ds->dev, > + "A DSA switch tree can have only one tagging > protocol\n"); > + return -EINVAL; > + } > + } else { > + dst->default_proto = default_proto; > + } > + > + /* See if the user wants to override that preference. */ > + if (user_protocol) { > + if (ds->ops->change_tag_protocol) { > + tag_ops = dsa_find_tagger_by_name(user_protocol); > + } else { > + dev_err(ds->dev, "Tag protocol cannot be modified\n"); > + return -EINVAL; > + } Your choice, but how about: if (!ds->ops->change_tag_protocol) { dev_err(ds->dev, "Tag protocol cannot be modified\n"); return -EINVAL; } tag_ops = dsa_find_tagger_by_name(user_protocol); > + } else { > + tag_ops = dsa_tag_driver_get(default_proto); > + } > + > + if (IS_ERR(tag_ops)) { > + if (PTR_ERR(tag_ops) == -ENOPROTOOPT) > + return -EPROBE_DEFER; > + > + dev_warn(ds->dev, "No tagger for this switch\n"); > + return PTR_ERR(tag_ops); > + } > > - tag_protocol = dsa_get_tag_protocol(dp, master); > if (dst->tag_ops) { > - if (dst->tag_ops->proto != tag_protocol) { > + if (dst->tag_ops != tag_ops) { > dev_err(ds->dev, > "A DSA switch tree can have only one tagging > protocol\n"); > + > + dsa_tag_driver_put(tag_ops); > return -EINVAL; > } > + > /* In the case of multiple CPU ports per switch, the tagging > - * protocol is still reference-counted only per switch tree, so > - * nothing to do here. > + * protocol is still reference-counted only per switch tree. > */ > + dsa_tag_driver_put(tag_ops); > } else { > - tag_ops = dsa_tag_driver_get(tag_protocol); > - if (IS_ERR(tag_ops)) { > - if (PTR_ERR(tag_ops) == -ENOPROTOOPT) > - return -EPROBE_DEFER; > - dev_warn(ds->dev, "No tagger for this switch\n"); > - dp->master = NULL; > - return PTR_ERR(tag_ops); > - } > - > dst->tag_ops = tag_ops; So at the end of dsa_port_parse_cpu, we have a dst->tag_ops which is temporarily out of sync with the driver. We call dsa_port_set_tag_protocol() with the new tagging protocol _before_ we call ds->ops->change_tag_protocol. But as opposed to dsa_switch_change_tag_proto(), if ds->ops->change_tag_protocol fails from the probe path, we treat it as a catastrophic error. So at the end there is no risk of having anything out of sync I believe. Maybe you should write this down in a comment? The logic is pretty convoluted and hard to follow. > } > > @@ -1117,12 +1176,14 @@ static int dsa_port_parse_of(struct dsa_port *dp, > struct device_node *dn) > > if (ethernet) { > struct net_device *master; > + const char *user_protocol; > > master = of_find_net_device_by_node(ethernet); > if (!master) > return -EPROBE_DEFER; > > - return dsa_port_parse_cpu(dp, master); > + user_protocol = of_get_property(dn, "dsa,tag-protocol", NULL); > + return dsa_port_parse_cpu(dp, master, user_protocol); > } > > if (link) > @@ -1234,7 +1295,7 @@ static int dsa_port_parse(struct dsa_port *dp, const > char *name, > > dev_put(master); > > - return dsa_port_parse_cpu(dp, master); > + return dsa_port_parse_cpu(dp, master, NULL); > } > > if (!strcmp(name, "dsa")) > -- > 2.25.1 >