net: dsa: add Renesas RZ/N1 switch tag driver

The switch that is present on the Renesas RZ/N1 SoC uses a specific
VLAN value followed by 6 bytes which contains forwarding configuration.
Signed-off-by: Clément Léger <clement.leger@bootlin.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/dsa.h

@@ -53,6 +53,7 @@ struct phylink_link_state;
 #define DSA_TAG_PROTO_SJA1110_VALUE		23
 #define DSA_TAG_PROTO_RTL8_4_VALUE		24
 #define DSA_TAG_PROTO_RTL8_4T_VALUE		25
+#define DSA_TAG_PROTO_RZN1_A5PSW_VALUE		26
 
 enum dsa_tag_protocol {
 	DSA_TAG_PROTO_NONE		= DSA_TAG_PROTO_NONE_VALUE,
@@ -81,6 +82,7 @@ enum dsa_tag_protocol {
 	DSA_TAG_PROTO_SJA1110		= DSA_TAG_PROTO_SJA1110_VALUE,
 	DSA_TAG_PROTO_RTL8_4		= DSA_TAG_PROTO_RTL8_4_VALUE,
 	DSA_TAG_PROTO_RTL8_4T		= DSA_TAG_PROTO_RTL8_4T_VALUE,
+	DSA_TAG_PROTO_RZN1_A5PSW	= DSA_TAG_PROTO_RZN1_A5PSW_VALUE,
 };
 
 struct dsa_switch;

include/uapi/linux/if_ether.h

@@ -116,6 +116,7 @@
 #define ETH_P_QINQ3	0x9300		/* deprecated QinQ VLAN [ NOT AN OFFICIALLY REGISTERED ID ] */
 #define ETH_P_EDSA	0xDADA		/* Ethertype DSA [ NOT AN OFFICIALLY REGISTERED ID ] */
 #define ETH_P_DSA_8021Q	0xDADB		/* Fake VLAN Header for DSA [ NOT AN OFFICIALLY REGISTERED ID ] */
+#define ETH_P_DSA_A5PSW	0xE001		/* A5PSW Tag Value [ NOT AN OFFICIALLY REGISTERED ID ] */
 #define ETH_P_IFE	0xED3E		/* ForCES inter-FE LFB type */
 #define ETH_P_AF_IUCV   0xFBFB		/* IBM af_iucv [ NOT AN OFFICIALLY REGISTERED ID ] */
 

net/dsa/Kconfig

@@ -132,6 +132,13 @@ config NET_DSA_TAG_RTL8_4
 	  Say Y or M if you want to enable support for tagging frames for Realtek
 	  switches with 8 byte protocol 4 tags, such as the Realtek RTL8365MB-VC.
 
+config NET_DSA_TAG_RZN1_A5PSW
+	tristate "Tag driver for Renesas RZ/N1 A5PSW switch"
+	help
+	  Say Y or M if you want to enable support for tagging frames for
+	  Renesas RZ/N1 embedded switch that uses an 8 byte tag located after
+	  destination MAC address.
+
 config NET_DSA_TAG_LAN9303
 	tristate "Tag driver for SMSC/Microchip LAN9303 family of switches"
 	help

net/dsa/Makefile

@@ -17,6 +17,7 @@ obj-$(CONFIG_NET_DSA_TAG_OCELOT_8021Q) += tag_ocelot_8021q.o
 obj-$(CONFIG_NET_DSA_TAG_QCA) += tag_qca.o
 obj-$(CONFIG_NET_DSA_TAG_RTL4_A) += tag_rtl4_a.o
 obj-$(CONFIG_NET_DSA_TAG_RTL8_4) += tag_rtl8_4.o
+obj-$(CONFIG_NET_DSA_TAG_RZN1_A5PSW) += tag_rzn1_a5psw.o
 obj-$(CONFIG_NET_DSA_TAG_SJA1105) += tag_sja1105.o
 obj-$(CONFIG_NET_DSA_TAG_TRAILER) += tag_trailer.o
 obj-$(CONFIG_NET_DSA_TAG_XRS700X) += tag_xrs700x.o

net/dsa/tag_rzn1_a5psw.c

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2022 Schneider Electric
+ *
+ * Clément Léger <clement.leger@bootlin.com>
+ */
+
+#include <linux/bitfield.h>
+#include <linux/etherdevice.h>
+#include <linux/if_ether.h>
+#include <net/dsa.h>
+
+#include "dsa_priv.h"
+
+/* To define the outgoing port and to discover the incoming port a TAG is
+ * inserted after Src MAC :
+ *
+ *       Dest MAC       Src MAC           TAG         Type
+ * ...| 1 2 3 4 5 6 | 1 2 3 4 5 6 | 1 2 3 4 5 6 7 8 | 1 2 |...
+ *                                |<--------------->|
+ *
+ * See struct a5psw_tag for layout
+ */
+
+#define ETH_P_DSA_A5PSW			0xE001
+#define A5PSW_TAG_LEN			8
+#define A5PSW_CTRL_DATA_FORCE_FORWARD	BIT(0)
+/* This is both used for xmit tag and rcv tagging */
+#define A5PSW_CTRL_DATA_PORT		GENMASK(3, 0)
+
+struct a5psw_tag {
+	__be16 ctrl_tag;
+	__be16 ctrl_data;
+	__be16 ctrl_data2_hi;
+	__be16 ctrl_data2_lo;
+};
+
+static struct sk_buff *a5psw_tag_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	struct dsa_port *dp = dsa_slave_to_port(dev);
+	struct a5psw_tag *ptag;
+	u32 data2_val;
+
+	BUILD_BUG_ON(sizeof(*ptag) != A5PSW_TAG_LEN);
+
+	/* The Ethernet switch we are interfaced with needs packets to be at
+	 * least 60 bytes otherwise they will be discarded when they enter the
+	 * switch port logic.
+	 */
+	if (__skb_put_padto(skb, ETH_ZLEN, false))
+		return NULL;
+
+	/* provide 'A5PSW_TAG_LEN' bytes additional space */
+	skb_push(skb, A5PSW_TAG_LEN);
+
+	/* make room between MACs and Ether-Type to insert tag */
+	dsa_alloc_etype_header(skb, A5PSW_TAG_LEN);
+
+	ptag = dsa_etype_header_pos_tx(skb);
+
+	data2_val = FIELD_PREP(A5PSW_CTRL_DATA_PORT, BIT(dp->index));
+	ptag->ctrl_tag = htons(ETH_P_DSA_A5PSW);
+	ptag->ctrl_data = htons(A5PSW_CTRL_DATA_FORCE_FORWARD);
+	ptag->ctrl_data2_lo = htons(data2_val);
+	ptag->ctrl_data2_hi = 0;
+
+	return skb;
+}
+
+static struct sk_buff *a5psw_tag_rcv(struct sk_buff *skb,
+				     struct net_device *dev)
+{
+	struct a5psw_tag *tag;
+	int port;
+
+	if (unlikely(!pskb_may_pull(skb, A5PSW_TAG_LEN))) {
+		dev_warn_ratelimited(&dev->dev,
+				     "Dropping packet, cannot pull\n");
+		return NULL;
+	}
+
+	tag = dsa_etype_header_pos_rx(skb);
+
+	if (tag->ctrl_tag != htons(ETH_P_DSA_A5PSW)) {
+		dev_warn_ratelimited(&dev->dev, "Dropping packet due to invalid TAG marker\n");
+		return NULL;
+	}
+
+	port = FIELD_GET(A5PSW_CTRL_DATA_PORT, ntohs(tag->ctrl_data));
+
+	skb->dev = dsa_master_find_slave(dev, 0, port);
+	if (!skb->dev)
+		return NULL;
+
+	skb_pull_rcsum(skb, A5PSW_TAG_LEN);
+	dsa_strip_etype_header(skb, A5PSW_TAG_LEN);
+
+	dsa_default_offload_fwd_mark(skb);
+
+	return skb;
+}
+
+static const struct dsa_device_ops a5psw_netdev_ops = {
+	.name	= "a5psw",
+	.proto	= DSA_TAG_PROTO_RZN1_A5PSW,
+	.xmit	= a5psw_tag_xmit,
+	.rcv	= a5psw_tag_rcv,
+	.needed_headroom = A5PSW_TAG_LEN,
+};
+
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_A5PSW);
+module_dsa_tag_driver(a5psw_netdev_ops);