netdev - [RFC net-next 9/9] net: dsa: mv88e6xxx: Forward offloading

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Date:   Mon, 26 Apr 2021 19:04:11 +0200
From:   Tobias Waldekranz <tobias@...dekranz.com>
To:     davem@...emloft.net, kuba@...nel.org
Cc:     andrew@...n.ch, vivien.didelot@...il.com, f.fainelli@...il.com,
        olteanv@...il.com, roopa@...dia.com, nikolay@...dia.com,
        jiri@...nulli.us, idosch@...sch.org, stephen@...workplumber.org,
        netdev@...r.kernel.org, bridge@...ts.linux-foundation.org
Subject: [RFC net-next 9/9] net: dsa: mv88e6xxx: Forward offloading

Allow the DSA tagger to generate FORWARD frames for offloaded skbs
sent from a bridge that we offload, allowing the switch to handle any
frame replication that may be required. This also means that source
address learning takes place on packets sent from the CPU, meaning
that return traffic no longer needs to be flooded as unknown unicast.

Signed-off-by: Tobias Waldekranz <tobias@...dekranz.com>
---
 drivers/net/dsa/mv88e6xxx/chip.c | 17 ++++++++++++++++
 net/dsa/tag_dsa.c                | 33 ++++++++++++++++++++++++--------
 2 files changed, 42 insertions(+), 8 deletions(-)

diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c
index 6975cf16da65..00ed1aa2a55a 100644
--- a/drivers/net/dsa/mv88e6xxx/chip.c
+++ b/drivers/net/dsa/mv88e6xxx/chip.c
@@ -6077,6 +6077,21 @@ static int mv88e6xxx_crosschip_lag_leave(struct dsa_switch *ds, int sw_index,
 	return err_sync ? : err_pvt;
 }
 
+static void *mv88e6xxx_dfwd_add_station(struct dsa_switch *ds, int port,
+					struct net_device *sb_dev)
+{
+	struct dsa_port *dp = dsa_to_port(ds, port);
+	struct mv88e6xxx_chip *chip = ds->priv;
+
+	if (!mv88e6xxx_has_pvt(chip))
+		return ERR_PTR(-EOPNOTSUPP);
+
+	if (sb_dev == dp->bridge_dev)
+		return sb_dev;
+
+	return ERR_PTR(-EOPNOTSUPP);
+}
+
 static const struct dsa_switch_ops mv88e6xxx_switch_ops = {
 	.get_tag_protocol	= mv88e6xxx_get_tag_protocol,
 	.change_tag_protocol	= mv88e6xxx_change_tag_protocol,
@@ -6138,6 +6153,7 @@ static const struct dsa_switch_ops mv88e6xxx_switch_ops = {
 	.crosschip_lag_change	= mv88e6xxx_crosschip_lag_change,
 	.crosschip_lag_join	= mv88e6xxx_crosschip_lag_join,
 	.crosschip_lag_leave	= mv88e6xxx_crosschip_lag_leave,
+	.dfwd_add_station	= mv88e6xxx_dfwd_add_station,
 };
 
 static int mv88e6xxx_register_switch(struct mv88e6xxx_chip *chip)
@@ -6156,6 +6172,7 @@ static int mv88e6xxx_register_switch(struct mv88e6xxx_chip *chip)
 	ds->ops = &mv88e6xxx_switch_ops;
 	ds->ageing_time_min = chip->info->age_time_coeff;
 	ds->ageing_time_max = chip->info->age_time_coeff * U8_MAX;
+	ds->num_tx_queues = 2;
 
 	/* Some chips support up to 32, but that requires enabling the
 	 * 5-bit port mode, which we do not support. 640k^W16 ought to
diff --git a/net/dsa/tag_dsa.c b/net/dsa/tag_dsa.c
index 7e7b7decdf39..09cdf77697b2 100644
--- a/net/dsa/tag_dsa.c
+++ b/net/dsa/tag_dsa.c
@@ -46,6 +46,7 @@
  */
 
 #include <linux/etherdevice.h>
+#include <linux/dsa/mv88e6xxx.h>
 #include <linux/list.h>
 #include <linux/slab.h>
 
@@ -126,7 +127,22 @@ static struct sk_buff *dsa_xmit_ll(struct sk_buff *skb, struct net_device *dev,
 				   u8 extra)
 {
 	struct dsa_port *dp = dsa_slave_to_port(dev);
+	u16 pvid = dp->pvid;
+	enum dsa_cmd cmd;
 	u8 *dsa_header;
+	u8 tag_dev, tag_port;
+
+	if (DSA_SKB_CB(skb)->sb_dev) {
+		cmd = DSA_CMD_FORWARD;
+		if (mv88e6xxx_dst_bridge_to_dsa(dp->ds->dst,
+						DSA_SKB_CB(skb)->sb_dev,
+						&tag_dev, &tag_port))
+			return NULL;
+	} else {
+		cmd = DSA_CMD_FROM_CPU;
+		tag_dev = dp->ds->index;
+		tag_port = dp->index;
+	}
 
 	if (skb->protocol == htons(ETH_P_8021Q)) {
 		if (extra) {
@@ -134,10 +150,10 @@ static struct sk_buff *dsa_xmit_ll(struct sk_buff *skb, struct net_device *dev,
 			memmove(skb->data, skb->data + extra, 2 * ETH_ALEN);
 		}
 
-		/* Construct tagged FROM_CPU DSA tag from 802.1Q tag. */
+		/* Construct tagged DSA tag from 802.1Q tag. */
 		dsa_header = skb->data + 2 * ETH_ALEN + extra;
-		dsa_header[0] = (DSA_CMD_FROM_CPU << 6) | 0x20 | dp->ds->index;
-		dsa_header[1] = dp->index << 3;
+		dsa_header[0] = (cmd << 6) | 0x20 | tag_dev;
+		dsa_header[1] = tag_port << 3;
 
 		/* Move CFI field from byte 2 to byte 1. */
 		if (dsa_header[2] & 0x10) {
@@ -148,12 +164,13 @@ static struct sk_buff *dsa_xmit_ll(struct sk_buff *skb, struct net_device *dev,
 		skb_push(skb, DSA_HLEN + extra);
 		memmove(skb->data, skb->data + DSA_HLEN + extra, 2 * ETH_ALEN);
 
-		/* Construct untagged FROM_CPU DSA tag. */
+		/* Construct untagged DSA tag. */
 		dsa_header = skb->data + 2 * ETH_ALEN + extra;
-		dsa_header[0] = (DSA_CMD_FROM_CPU << 6) | dp->ds->index;
-		dsa_header[1] = dp->index << 3;
-		dsa_header[2] = 0x00;
-		dsa_header[3] = 0x00;
+
+		dsa_header[0] = (cmd << 6) | tag_dev;
+		dsa_header[1] = tag_port << 3;
+		dsa_header[2] = pvid >> 8;
+		dsa_header[3] = pvid & 0xff;
 	}
 
 	return skb;
-- 
2.25.1