net/sched: cbs: Set default link speed to 10 Mbps in cbs_set_port_rate

The discussion to be made is absolutely the same as in the case of
previous patch ("taprio: Set default link speed to 10 Mbps in
taprio_set_picos_per_byte"). Nothing is lost when setting a default.

Cc: Leandro Dorileo <leandro.maciel.dorileo@intel.com>
Fixes: e0a7683d ("net/sched: cbs: fix port_rate miscalculation")
Acked-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/sch_cbs.c

@@ -181,11 +181,6 @@ static struct sk_buff *cbs_dequeue_soft(struct Qdisc *sch)
 	s64 credits;
 	int len;
 
-	if (atomic64_read(&q->port_rate) == -1) {
-		WARN_ONCE(1, "cbs: dequeue() called with unknown port rate.");
-		return NULL;
-	}
-
 	if (q->credits < 0) {
 		credits = timediff_to_credits(now - q->last, q->idleslope);
 
@@ -303,11 +298,19 @@ static int cbs_enable_offload(struct net_device *dev, struct cbs_sched_data *q,
 static void cbs_set_port_rate(struct net_device *dev, struct cbs_sched_data *q)
 {
 	struct ethtool_link_ksettings ecmd;
+	int speed = SPEED_10;
 	int port_rate = -1;
+	int err;
+
+	err = __ethtool_get_link_ksettings(dev, &ecmd);
+	if (err < 0)
+		goto skip;
+
+	if (ecmd.base.speed != SPEED_UNKNOWN)
+		speed = ecmd.base.speed;
 
-	if (!__ethtool_get_link_ksettings(dev, &ecmd) &&
-	    ecmd.base.speed != SPEED_UNKNOWN)
-		port_rate = ecmd.base.speed * 1000 * BYTES_PER_KBIT;
+skip:
+	port_rate = speed * 1000 * BYTES_PER_KBIT;
 
 	atomic64_set(&q->port_rate, port_rate);
 	netdev_dbg(dev, "cbs: set %s's port_rate to: %lld, linkspeed: %d\n",