net: dsa: report and change port dscp priority using dcbnl

Similar to the port-based default priority, IEEE 802.1Q-2018 allows the
Application Priority Table to define QoS classes (0 to 7) per IP DSCP
value (0 to 63).

In the absence of an app table entry for a packet with DSCP value X,
QoS classification for that packet falls back to other methods (VLAN PCP
or port-based default). The presence of an app table for DSCP value X
with priority Y makes the hardware classify the packet to QoS class Y.

As opposed to the default-prio where DSA exposes only a "set" in
dsa_switch_ops (because the port-based default is the fallback, it
always exists, either implicitly or explicitly), for DSCP priorities we
expose an "add" and a "del". The addition of a DSCP entry means trusting
that DSCP priority, the deletion means ignoring it.

Drivers that already trust (at least some) DSCP values can describe
their configuration in dsa_switch_ops :: port_get_dscp_prio(), which is
called for each DSCP value from 0 to 63.

Again, there can be more than one dcbnl app table entry for the same
DSCP value, DSA chooses the one with the largest configured priority.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/dsa.h

@@ -898,6 +898,11 @@ struct dsa_switch_ops {
 	int	(*port_get_default_prio)(struct dsa_switch *ds, int port);
 	int	(*port_set_default_prio)(struct dsa_switch *ds, int port,
 					 u8 prio);
+	int	(*port_get_dscp_prio)(struct dsa_switch *ds, int port, u8 dscp);
+	int	(*port_add_dscp_prio)(struct dsa_switch *ds, int port, u8 dscp,
+				      u8 prio);
+	int	(*port_del_dscp_prio)(struct dsa_switch *ds, int port, u8 dscp,
+				      u8 prio);
 
 	/*
 	 * Suspend and resume

net/dsa/slave.c

@@ -1880,6 +1880,40 @@ dsa_slave_dcbnl_set_default_prio(struct net_device *dev, struct dcb_app *app)
 	return 0;
 }
 
+static int __maybe_unused
+dsa_slave_dcbnl_add_dscp_prio(struct net_device *dev, struct dcb_app *app)
+{
+	struct dsa_port *dp = dsa_slave_to_port(dev);
+	struct dsa_switch *ds = dp->ds;
+	unsigned long mask, new_prio;
+	int err, port = dp->index;
+	u8 dscp = app->protocol;
+
+	if (!ds->ops->port_add_dscp_prio)
+		return -EOPNOTSUPP;
+
+	if (dscp >= 64) {
+		netdev_err(dev, "DSCP APP entry with protocol value %u is invalid\n",
+			   dscp);
+		return -EINVAL;
+	}
+
+	err = dcb_ieee_setapp(dev, app);
+	if (err)
+		return err;
+
+	mask = dcb_ieee_getapp_mask(dev, app);
+	new_prio = __fls(mask);
+
+	err = ds->ops->port_add_dscp_prio(ds, port, dscp, new_prio);
+	if (err) {
+		dcb_ieee_delapp(dev, app);
+		return err;
+	}
+
+	return 0;
+}
+
 static int __maybe_unused dsa_slave_dcbnl_ieee_setapp(struct net_device *dev,
 						      struct dcb_app *app)
 {
@@ -1892,6 +1926,8 @@ static int __maybe_unused dsa_slave_dcbnl_ieee_setapp(struct net_device *dev,
 			return -EOPNOTSUPP;
 		}
 		break;
+	case IEEE_8021QAZ_APP_SEL_DSCP:
+		return dsa_slave_dcbnl_add_dscp_prio(dev, app);
 	default:
 		return -EOPNOTSUPP;
 	}
@@ -1924,6 +1960,30 @@ dsa_slave_dcbnl_del_default_prio(struct net_device *dev, struct dcb_app *app)
 	return 0;
 }
 
+static int __maybe_unused
+dsa_slave_dcbnl_del_dscp_prio(struct net_device *dev, struct dcb_app *app)
+{
+	struct dsa_port *dp = dsa_slave_to_port(dev);
+	struct dsa_switch *ds = dp->ds;
+	int err, port = dp->index;
+	u8 dscp = app->protocol;
+
+	if (!ds->ops->port_del_dscp_prio)
+		return -EOPNOTSUPP;
+
+	err = dcb_ieee_delapp(dev, app);
+	if (err)
+		return err;
+
+	err = ds->ops->port_del_dscp_prio(ds, port, dscp, app->priority);
+	if (err) {
+		dcb_ieee_setapp(dev, app);
+		return err;
+	}
+
+	return 0;
+}
+
 static int __maybe_unused dsa_slave_dcbnl_ieee_delapp(struct net_device *dev,
 						      struct dcb_app *app)
 {
@@ -1936,6 +1996,8 @@ static int __maybe_unused dsa_slave_dcbnl_ieee_delapp(struct net_device *dev,
 			return -EOPNOTSUPP;
 		}
 		break;
+	case IEEE_8021QAZ_APP_SEL_DSCP:
+		return dsa_slave_dcbnl_del_dscp_prio(dev, app);
 	default:
 		return -EOPNOTSUPP;
 	}
@@ -1967,6 +2029,30 @@ static int dsa_slave_dcbnl_init(struct net_device *dev)
 			return err;
 	}
 
+	if (ds->ops->port_get_dscp_prio) {
+		int protocol;
+
+		for (protocol = 0; protocol < 64; protocol++) {
+			struct dcb_app app = {
+				.selector = IEEE_8021QAZ_APP_SEL_DSCP,
+				.protocol = protocol,
+			};
+			int prio;
+
+			prio = ds->ops->port_get_dscp_prio(ds, port, protocol);
+			if (prio == -EOPNOTSUPP)
+				continue;
+			if (prio < 0)
+				return prio;
+
+			app.priority = prio;
+
+			err = dcb_ieee_setapp(dev, &app);
+			if (err)
+				return err;
+		}
+	}
+
 	return 0;
 }