net: dsa: add support switches global DSCP priority mapping

Some switches like Microchip KSZ variants do not support per port DSCP
priority configuration. Instead there is a global DSCP mapping table.

To handle it, we will accept set/del request to any of user ports to
make global configuration and update dcb app entries for all other
ports.
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/dsa.h

@@ -433,6 +433,11 @@ struct dsa_switch {
 	 */
 	u32			fdb_isolation:1;
 
+	/* Drivers that have global DSCP mapping settings must set this to
+	 * true to automatically apply the settings to all ports.
+	 */
+	u32			dscp_prio_mapping_is_global:1;
+
 	/* Listener for switch fabric events */
 	struct notifier_block	nb;
 
@@ -586,6 +591,10 @@ static inline bool dsa_is_user_port(struct dsa_switch *ds, int p)
 	dsa_switch_for_each_port((_dp), (_ds)) \
 		if (dsa_port_is_user((_dp)))
 
+#define dsa_switch_for_each_user_port_continue_reverse(_dp, _ds) \
+	dsa_switch_for_each_port_continue_reverse((_dp), (_ds)) \
+		if (dsa_port_is_user((_dp)))
+
 #define dsa_switch_for_each_cpu_port(_dp, _ds) \
 	dsa_switch_for_each_port((_dp), (_ds)) \
 		if (dsa_port_is_cpu((_dp)))

net/dsa/user.c

@@ -2189,6 +2189,58 @@ dsa_user_dcbnl_set_default_prio(struct net_device *dev, struct dcb_app *app)
 	return 0;
 }
 
+/* Update the DSCP prio entries on all user ports of the switch in case
+ * the switch supports global DSCP prio instead of per port DSCP prios.
+ */
+static int dsa_user_dcbnl_ieee_global_dscp_setdel(struct net_device *dev,
+						  struct dcb_app *app, bool del)
+{
+	int (*setdel)(struct net_device *dev, struct dcb_app *app);
+	struct dsa_port *dp = dsa_user_to_port(dev);
+	struct dsa_switch *ds = dp->ds;
+	struct dsa_port *other_dp;
+	int err, restore_err;
+
+	if (del)
+		setdel = dcb_ieee_delapp;
+	else
+		setdel = dcb_ieee_setapp;
+
+	dsa_switch_for_each_user_port(other_dp, ds) {
+		struct net_device *user = other_dp->user;
+
+		if (!user || user == dev)
+			continue;
+
+		err = setdel(user, app);
+		if (err)
+			goto err_try_to_restore;
+	}
+
+	return 0;
+
+err_try_to_restore:
+
+	/* Revert logic to restore previous state of app entries */
+	if (!del)
+		setdel = dcb_ieee_delapp;
+	else
+		setdel = dcb_ieee_setapp;
+
+	dsa_switch_for_each_user_port_continue_reverse(other_dp, ds) {
+		struct net_device *user = other_dp->user;
+
+		if (!user || user == dev)
+			continue;
+
+		restore_err = setdel(user, app);
+		if (restore_err)
+			netdev_err(user, "Failed to restore DSCP prio entry configuration\n");
+	}
+
+	return err;
+}
+
 static int __maybe_unused
 dsa_user_dcbnl_add_dscp_prio(struct net_device *dev, struct dcb_app *app)
 {
@@ -2220,6 +2272,17 @@ dsa_user_dcbnl_add_dscp_prio(struct net_device *dev, struct dcb_app *app)
 		return err;
 	}
 
+	if (!ds->dscp_prio_mapping_is_global)
+		return 0;
+
+	err = dsa_user_dcbnl_ieee_global_dscp_setdel(dev, app, false);
+	if (err) {
+		if (ds->ops->port_del_dscp_prio)
+			ds->ops->port_del_dscp_prio(ds, port, dscp, new_prio);
+		dcb_ieee_delapp(dev, app);
+		return err;
+	}
+
 	return 0;
 }
 
@@ -2290,6 +2353,18 @@ dsa_user_dcbnl_del_dscp_prio(struct net_device *dev, struct dcb_app *app)
 		return err;
 	}
 
+	if (!ds->dscp_prio_mapping_is_global)
+		return 0;
+
+	err = dsa_user_dcbnl_ieee_global_dscp_setdel(dev, app, true);
+	if (err) {
+		if (ds->ops->port_add_dscp_prio)
+			ds->ops->port_add_dscp_prio(ds, port, dscp,
+						    app->priority);
+		dcb_ieee_setapp(dev, app);
+		return err;
+	}
+
 	return 0;
 }