[PATCH net-next v3 02/12] net: dsa: add Renesas RZ/N1 switch tag driver

[Clément Léger]

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@xxxxxxxxxxx>
---
 include/net/dsa.h        |   2 +
 net/dsa/Kconfig          |   7 +++
 net/dsa/Makefile         |   1 +
 net/dsa/tag_rzn1_a5psw.c | 114 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 124 insertions(+)
 create mode 100644 net/dsa/tag_rzn1_a5psw.c

diff --git a/include/net/dsa.h b/include/net/dsa.h
index d9da32aacbf1..9aaaa7deb102 100644
--- a/include/net/dsa.h
+++ b/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;
diff --git a/net/dsa/Kconfig b/net/dsa/Kconfig
index 8cb87b5067ee..e22f33d7cf60 100644
--- a/net/dsa/Kconfig
+++ b/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 a 8 byte tag located after
+	  destination MAC address.
+
 config NET_DSA_TAG_LAN9303
 	tristate "Tag driver for SMSC/Microchip LAN9303 family of switches"
 	help
diff --git a/net/dsa/Makefile b/net/dsa/Makefile
index 9f75820e7c98..af28c24ead18 100644
--- a/net/dsa/Makefile
+++ b/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
diff --git a/net/dsa/tag_rzn1_a5psw.c b/net/dsa/tag_rzn1_a5psw.c
new file mode 100644
index 000000000000..87177682eb54
--- /dev/null
+++ b/net/dsa/tag_rzn1_a5psw.c
@@ -0,0 +1,114 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2022 Schneider Electric
+ *
+ * Clément Léger <clement.leger@xxxxxxxxxxx>
+ */
+
+#include <linux/bitfield.h>
+#include <linux/etherdevice.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 A5PSW_TAG_VALUE			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 64 bytes (including FCS) otherwise they will be discarded when
+	 * they enter the switch port logic. When tagging is enabled, we need
+	 * to make sure that packets are at least 70 bytes (including FCS and
+	 * tag).
+	 */
+	if (__skb_put_padto(skb, ETH_ZLEN + ETH_FCS_LEN + A5PSW_TAG_LEN, 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(A5PSW_TAG_VALUE);
+	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(A5PSW_TAG_VALUE)) {
+		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);
-- 
2.34.1