net: mscc: ocelot: fix QoS class for injected packets with "ocelot-8021q"

There are 2 distinct code paths (listed below) in the source code which
set up an injection header for Ocelot(-like) switches. Code path (2)
lacks the QoS class and source port being set correctly. Especially the
improper QoS classification is a problem for the "ocelot-8021q"
alternative DSA tagging protocol, because we support tc-taprio and each
packet needs to be scheduled precisely through its time slot. This
includes PTP, which is normally assigned to a traffic class other than
0, but would be sent through TC 0 nonetheless.

The code paths are:

(1) ocelot_xmit_common() from net/dsa/tag_ocelot.c - called only by the
standard "ocelot" DSA tagging protocol which uses NPI-based
injection - sets up bit fields in the tag manually to account for
a small difference (destination port offset) between Ocelot and
Seville. Namely, ocelot_ifh_set_dest() is omitted out of
ocelot_xmit_common(), because there's also seville_ifh_set_dest().

(2) ocelot_ifh_set_basic(), called by:
- ocelot_fdma_prepare_skb() for FDMA transmission of the ocelot
switchdev driver
- ocelot_port_xmit() -> ocelot_port_inject_frame() for
register-based transmission of the ocelot switchdev driver
- felix_port_deferred_xmit() -> ocelot_port_inject_frame() for the
DSA tagger ocelot-8021q when it must transmit PTP frames (also
through register-based injection).
sets the bit fields according to its own logic.

The problem is that (2) doesn't call ocelot_ifh_set_qos_class().
Copying that logic from ocelot_xmit_common() fixes that.

Unfortunately, although desirable, it is not easily possible to
de-duplicate code paths (1) and (2), and make net/dsa/tag_ocelot.c
directly call ocelot_ifh_set_basic()), because of the ocelot/seville
difference. This is the "minimal" fix with some logic duplicated (but
at least more consolidated).

Fixes: 0a6f17c6ae21 ("net: dsa: tag_ocelot_8021q: add support for PTP timestamping")
Signed-off-by: Vladimir Oltean <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ethernet/mscc/ocelot.c

···
 			  u32 rew_op, struct sk_buff *skb)
 {
 	struct ocelot_port *ocelot_port = ocelot->ports[port];
+	struct net_device *dev = skb->dev;
 	u64 vlan_tci, tag_type;
+	int qos_class;
 
 	ocelot_xmit_get_vlan_info(skb, ocelot_port->bridge, &vlan_tci,
 				  &tag_type);
 
+	qos_class = netdev_get_num_tc(dev) ?
+		    netdev_get_prio_tc_map(dev, skb->priority) : skb->priority;
+
+	memset(ifh, 0, OCELOT_TAG_LEN);
 	ocelot_ifh_set_bypass(ifh, 1);
+	ocelot_ifh_set_src(ifh, BIT_ULL(ocelot->num_phys_ports));
 	ocelot_ifh_set_dest(ifh, BIT_ULL(port));
+	ocelot_ifh_set_qos_class(ifh, qos_class);
 	ocelot_ifh_set_tag_type(ifh, tag_type);
 	ocelot_ifh_set_vlan_tci(ifh, vlan_tci);
 	if (rew_op)
···
 void ocelot_port_inject_frame(struct ocelot *ocelot, int port, int grp,
 			      u32 rew_op, struct sk_buff *skb)
 {
-	u32 ifh[OCELOT_TAG_LEN / 4] = {0};
+	u32 ifh[OCELOT_TAG_LEN / 4];
 	unsigned int i, count, last;
 
 	ocelot_write_rix(ocelot, QS_INJ_CTRL_GAP_SIZE(1) |

drivers/net/ethernet/mscc/ocelot_fdma.c

···
 
 	ifh = skb_push(skb, OCELOT_TAG_LEN);
 	skb_put(skb, ETH_FCS_LEN);
-	memset(ifh, 0, OCELOT_TAG_LEN);
 	ocelot_ifh_set_basic(ifh, ocelot, port, rew_op, skb);
 
 	return 0;