net: dsa: use ports list to setup default CPU port

Use the new ports list instead of iterating over switches and their
ports when setting up the default CPU port. Unassign it on teardown.

Now that we can iterate over multiple CPU ports, remove dst->cpu_dp.

At the same time, provide a better error message for CPU-less tree.
Signed-off-by: NVivien Didelot <vivien.didelot@gmail.com>
Reviewed-by: NFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: NJakub Kicinski <jakub.kicinski@netronome.com>

include/net/dsa.h

@@ -120,11 +120,6 @@ struct dsa_switch_tree {
 	 */
 	struct dsa_platform_data	*pd;
 
-	/*
-	 * The switch port to which the CPU is attached.
-	 */
-	struct dsa_port		*cpu_dp;
-
 	/* List of switch ports */
 	struct list_head ports;
 

net/dsa/dsa2.c

@@ -197,38 +197,29 @@ static struct dsa_port *dsa_tree_find_first_cpu(struct dsa_switch_tree *dst)
 
 static int dsa_tree_setup_default_cpu(struct dsa_switch_tree *dst)
 {
-	struct dsa_switch *ds;
-	struct dsa_port *dp;
-	int device, port;
+	struct dsa_port *cpu_dp, *dp;
 
-	/* DSA currently only supports a single CPU port */
-	dst->cpu_dp = dsa_tree_find_first_cpu(dst);
-	if (!dst->cpu_dp) {
-		pr_warn("Tree has no master device\n");
+	cpu_dp = dsa_tree_find_first_cpu(dst);
+	if (!cpu_dp) {
+		pr_err("DSA: tree %d has no CPU port\n", dst->index);
 		return -EINVAL;
 	}
 
 	/* Assign the default CPU port to all ports of the fabric */
-	for (device = 0; device < DSA_MAX_SWITCHES; device++) {
-		ds = dst->ds[device];
-		if (!ds)
-			continue;
-
-		for (port = 0; port < ds->num_ports; port++) {
-			dp = &ds->ports[port];
-
-			if (dsa_port_is_user(dp) || dsa_port_is_dsa(dp))
-				dp->cpu_dp = dst->cpu_dp;
-		}
-	}
+	list_for_each_entry(dp, &dst->ports, list)
+		if (dsa_port_is_user(dp) || dsa_port_is_dsa(dp))
+			dp->cpu_dp = cpu_dp;
 
 	return 0;
 }
 
 static void dsa_tree_teardown_default_cpu(struct dsa_switch_tree *dst)
 {
-	/* DSA currently only supports a single CPU port */
-	dst->cpu_dp = NULL;
+	struct dsa_port *dp;
+
+	list_for_each_entry(dp, &dst->ports, list)
+		if (dsa_port_is_user(dp) || dsa_port_is_dsa(dp))
+			dp->cpu_dp = NULL;
 }
 
 static int dsa_port_setup(struct dsa_port *dp)