net: dsa: sja1105: Advertise the 8 TX queues

This is a preparation patch for the tc-taprio offload (and potentially
for other future offloads such as tc-mqprio).

Instead of looking directly at skb->priority during xmit, let's get the
netdev queue and the queue-to-traffic-class mapping, and put the
resulting traffic class into the dsa_8021q PCP field. The switch is
configured with a 1-to-1 PCP-to-ingress-queue-to-egress-queue mapping
(see vlan_pmap in sja1105_main.c), so the effect is that we can inject
into a front-panel's egress traffic class through VLAN tagging from
Linux, completely transparently.

Unfortunately the switch doesn't look at the VLAN PCP in the case of
management traffic to/from the CPU (link-local frames at
01-80-C2-xx-xx-xx or 01-1B-19-xx-xx-xx) so we can't alter the
transmission queue of this type of traffic on a frame-by-frame basis. It
is only selected through the "hostprio" setting which ATM is harcoded in
the driver to 7.
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/sja1105/sja1105_main.c

@@ -384,7 +384,9 @@ static int sja1105_init_general_params(struct sja1105_private *priv)
 		/* Disallow dynamic changing of the mirror port */
 		.mirr_ptacu = 0,
 		.switchid = priv->ds->index,
-		/* Priority queue for link-local frames trapped to CPU */
+		/* Priority queue for link-local management frames
+		 * (both ingress to and egress from CPU - PTP, STP etc)
+		 */
 		.hostprio = 7,
 		.mac_fltres1 = SJA1105_LINKLOCAL_FILTER_A,
 		.mac_flt1    = SJA1105_LINKLOCAL_FILTER_A_MASK,
@@ -1711,6 +1713,9 @@ static int sja1105_setup(struct dsa_switch *ds)
 	 */
 	ds->vlan_filtering_is_global = true;
 
+	/* Advertise the 8 egress queues */
+	ds->num_tx_queues = SJA1105_NUM_TC;
+
 	/* The DSA/switchdev model brings up switch ports in standalone mode by
 	 * default, and that means vlan_filtering is 0 since they're not under
 	 * a bridge, so it's safe to set up switch tagging at this time.

net/dsa/tag_sja1105.c

@@ -89,7 +89,8 @@ static struct sk_buff *sja1105_xmit(struct sk_buff *skb,
 	struct dsa_port *dp = dsa_slave_to_port(netdev);
 	struct dsa_switch *ds = dp->ds;
 	u16 tx_vid = dsa_8021q_tx_vid(ds, dp->index);
-	u8 pcp = skb->priority;
+	u16 queue_mapping = skb_get_queue_mapping(skb);
+	u8 pcp = netdev_txq_to_tc(netdev, queue_mapping);
 
 	/* Transmitting management traffic does not rely upon switch tagging,
 	 * but instead SPI-installed management routes. Part 2 of this