net: dsa: add a second tagger for Ocelot switches based on tag_8021q

There are use cases for which the existing tagger, based on the NPI
(Node Processor Interface) functionality, is insufficient.

Namely:
- Frames injected through the NPI port bypass the frame analyzer, so no
  source address learning is performed, no TSN stream classification,
  etc.
- Flow control is not functional over an NPI port (PAUSE frames are
  encapsulated in the same Extraction Frame Header as all other frames)
- There can be at most one NPI port configured for an Ocelot switch. But
  in NXP LS1028A and T1040 there are two Ethernet CPU ports. The non-NPI
  port is currently either disabled, or operated as a plain user port
  (albeit an internally-facing one). Having the ability to configure the
  two CPU ports symmetrically could pave the way for e.g. creating a LAG
  between them, to increase bandwidth seamlessly for the system.

So there is a desire to have an alternative to the NPI mode. This change
keeps the default tagger for the Seville and Felix switches as "ocelot",
but it can be changed via the following device attribute:

echo ocelot-8021q > /sys/class/<dsa-master>/dsa/tagging

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 68 insertions, 0 deletions

diff --git a/net/dsa/tag_ocelot_8021q.c b/net/dsa/tag_ocelot_8021q.c
new file mode 100644
index 000000000000..8991ebf098a3
--- /dev/null
+++ b/net/dsa/tag_ocelot_8021q.c
@@ -0,0 +1,68 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright 2020-2021 NXP Semiconductors
+ *
+ * An implementation of the software-defined tag_8021q.c tagger format, which
+ * also preserves full functionality under a vlan_filtering bridge. It does
+ * this by using the TCAM engines for:
+ * - pushing the RX VLAN as a second, outer tag, on egress towards the CPU port
+ * - redirecting towards the correct front port based on TX VLAN and popping
+ *   that on egress
+ */
+#include <linux/dsa/8021q.h>
+#include "dsa_priv.h"
+
+static struct sk_buff *ocelot_xmit(struct sk_buff *skb,
+				   struct net_device *netdev)
+{
+	struct dsa_port *dp = dsa_slave_to_port(netdev);
+	u16 tx_vid = dsa_8021q_tx_vid(dp->ds, dp->index);
+	u16 queue_mapping = skb_get_queue_mapping(skb);
+	u8 pcp = netdev_txq_to_tc(netdev, queue_mapping);
+
+	return dsa_8021q_xmit(skb, netdev, ETH_P_8021Q,
+			      ((pcp << VLAN_PRIO_SHIFT) | tx_vid));
+}
+
+static struct sk_buff *ocelot_rcv(struct sk_buff *skb,
+				  struct net_device *netdev,
+				  struct packet_type *pt)
+{
+	int src_port, switch_id, qos_class;
+	u16 vid, tci;
+
+	skb_push_rcsum(skb, ETH_HLEN);
+	if (skb_vlan_tag_present(skb)) {
+		tci = skb_vlan_tag_get(skb);
+		__vlan_hwaccel_clear_tag(skb);
+	} else {
+		__skb_vlan_pop(skb, &tci);
+	}
+	skb_pull_rcsum(skb, ETH_HLEN);
+
+	vid = tci & VLAN_VID_MASK;
+	src_port = dsa_8021q_rx_source_port(vid);
+	switch_id = dsa_8021q_rx_switch_id(vid);
+	qos_class = (tci & VLAN_PRIO_MASK) >> VLAN_PRIO_SHIFT;
+
+	skb->dev = dsa_master_find_slave(netdev, switch_id, src_port);
+	if (!skb->dev)
+		return NULL;
+
+	skb->offload_fwd_mark = 1;
+	skb->priority = qos_class;
+
+	return skb;
+}
+
+static const struct dsa_device_ops ocelot_8021q_netdev_ops = {
+	.name			= "ocelot-8021q",
+	.proto			= DSA_TAG_PROTO_OCELOT_8021Q,
+	.xmit			= ocelot_xmit,
+	.rcv			= ocelot_rcv,
+	.overhead		= VLAN_HLEN,
+};
+
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_OCELOT_8021Q);
+
+module_dsa_tag_driver(ocelot_8021q_netdev_ops);