net: dsa: Add Lantiq / Intel GSWIP tag support

This handles the tag added by the PMAC on the VRX200 SoC line.

The GSWIP uses internally a GSWIP special tag which is located after the
Ethernet header. The PMAC which connects the GSWIP to the CPU converts
this special tag used by the GSWIP into the PMAC special tag which is
added in front of the Ethernet header.

This was tested with GSWIP 2.1 found in the VRX200 SoCs, other GSWIP
versions use slightly different PMAC special tags.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

MAINTAINERS

@@ -8167,6 +8167,12 @@ S:	Maintained
 F:	net/l3mdev
 F:	include/net/l3mdev.h
 
+LANTIQ / INTEL Ethernet drivers
+M:	Hauke Mehrtens <hauke@hauke-m.de>
+L:	netdev@vger.kernel.org
+S:	Maintained
+F:	net/dsa/tag_gswip.c
+
 LANTIQ MIPS ARCHITECTURE
 M:	John Crispin <john@phrozen.org>
 L:	linux-mips@linux-mips.org

include/net/dsa.h

@@ -35,6 +35,7 @@ enum dsa_tag_protocol {
 	DSA_TAG_PROTO_BRCM_PREPEND,
 	DSA_TAG_PROTO_DSA,
 	DSA_TAG_PROTO_EDSA,
+	DSA_TAG_PROTO_GSWIP,
 	DSA_TAG_PROTO_KSZ,
 	DSA_TAG_PROTO_LAN9303,
 	DSA_TAG_PROTO_MTK,

net/dsa/Kconfig

@@ -38,6 +38,9 @@ config NET_DSA_TAG_DSA
 config NET_DSA_TAG_EDSA
 	bool
 
+config NET_DSA_TAG_GSWIP
+	bool
+
 config NET_DSA_TAG_KSZ
 	bool
 

net/dsa/Makefile

@@ -9,6 +9,7 @@ dsa_core-$(CONFIG_NET_DSA_TAG_BRCM) += tag_brcm.o
 dsa_core-$(CONFIG_NET_DSA_TAG_BRCM_PREPEND) += tag_brcm.o
 dsa_core-$(CONFIG_NET_DSA_TAG_DSA) += tag_dsa.o
 dsa_core-$(CONFIG_NET_DSA_TAG_EDSA) += tag_edsa.o
+dsa_core-$(CONFIG_NET_DSA_TAG_GSWIP) += tag_gswip.o
 dsa_core-$(CONFIG_NET_DSA_TAG_KSZ) += tag_ksz.o
 dsa_core-$(CONFIG_NET_DSA_TAG_LAN9303) += tag_lan9303.o
 dsa_core-$(CONFIG_NET_DSA_TAG_MTK) += tag_mtk.o

net/dsa/dsa.c

@@ -52,6 +52,9 @@ const struct dsa_device_ops *dsa_device_ops[DSA_TAG_LAST] = {
 #ifdef CONFIG_NET_DSA_TAG_EDSA
 	[DSA_TAG_PROTO_EDSA] = &edsa_netdev_ops,
 #endif
+#ifdef CONFIG_NET_DSA_TAG_GSWIP
+	[DSA_TAG_PROTO_GSWIP] = &gswip_netdev_ops,
+#endif
 #ifdef CONFIG_NET_DSA_TAG_KSZ
 	[DSA_TAG_PROTO_KSZ] = &ksz_netdev_ops,
 #endif

net/dsa/dsa_priv.h

@@ -206,6 +206,9 @@ extern const struct dsa_device_ops dsa_netdev_ops;
 /* tag_edsa.c */
 extern const struct dsa_device_ops edsa_netdev_ops;
 
+/* tag_gswip.c */
+extern const struct dsa_device_ops gswip_netdev_ops;
+
 /* tag_ksz.c */
 extern const struct dsa_device_ops ksz_netdev_ops;
 

net/dsa/tag_gswip.c

@@ -0,0 +1,109 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Intel / Lantiq GSWIP V2.0 PMAC tag support
+ *
+ * Copyright (C) 2017 - 2018 Hauke Mehrtens <hauke@hauke-m.de>
+ */
+
+#include <linux/bitops.h>
+#include <linux/etherdevice.h>
+#include <linux/skbuff.h>
+#include <net/dsa.h>
+
+#include "dsa_priv.h"
+
+#define GSWIP_TX_HEADER_LEN		4
+
+/* special tag in TX path header */
+/* Byte 0 */
+#define GSWIP_TX_SLPID_SHIFT		0	/* source port ID */
+#define  GSWIP_TX_SLPID_CPU		2
+#define  GSWIP_TX_SLPID_APP1		3
+#define  GSWIP_TX_SLPID_APP2		4
+#define  GSWIP_TX_SLPID_APP3		5
+#define  GSWIP_TX_SLPID_APP4		6
+#define  GSWIP_TX_SLPID_APP5		7
+
+/* Byte 1 */
+#define GSWIP_TX_CRCGEN_DIS		BIT(7)
+#define GSWIP_TX_DPID_SHIFT		0	/* destination group ID */
+#define  GSWIP_TX_DPID_ELAN		0
+#define  GSWIP_TX_DPID_EWAN		1
+#define  GSWIP_TX_DPID_CPU		2
+#define  GSWIP_TX_DPID_APP1		3
+#define  GSWIP_TX_DPID_APP2		4
+#define  GSWIP_TX_DPID_APP3		5
+#define  GSWIP_TX_DPID_APP4		6
+#define  GSWIP_TX_DPID_APP5		7
+
+/* Byte 2 */
+#define GSWIP_TX_PORT_MAP_EN		BIT(7)
+#define GSWIP_TX_PORT_MAP_SEL		BIT(6)
+#define GSWIP_TX_LRN_DIS		BIT(5)
+#define GSWIP_TX_CLASS_EN		BIT(4)
+#define GSWIP_TX_CLASS_SHIFT		0
+#define GSWIP_TX_CLASS_MASK		GENMASK(3, 0)
+
+/* Byte 3 */
+#define GSWIP_TX_DPID_EN		BIT(0)
+#define GSWIP_TX_PORT_MAP_SHIFT		1
+#define GSWIP_TX_PORT_MAP_MASK		GENMASK(6, 1)
+
+#define GSWIP_RX_HEADER_LEN	8
+
+/* special tag in RX path header */
+/* Byte 7 */
+#define GSWIP_RX_SPPID_SHIFT		4
+#define GSWIP_RX_SPPID_MASK		GENMASK(6, 4)
+
+static struct sk_buff *gswip_tag_xmit(struct sk_buff *skb,
+				      struct net_device *dev)
+{
+	struct dsa_port *dp = dsa_slave_to_port(dev);
+	int err;
+	u8 *gswip_tag;
+
+	err = skb_cow_head(skb, GSWIP_TX_HEADER_LEN);
+	if (err)
+		return NULL;
+
+	skb_push(skb, GSWIP_TX_HEADER_LEN);
+
+	gswip_tag = skb->data;
+	gswip_tag[0] = GSWIP_TX_SLPID_CPU;
+	gswip_tag[1] = GSWIP_TX_DPID_ELAN;
+	gswip_tag[2] = GSWIP_TX_PORT_MAP_EN | GSWIP_TX_PORT_MAP_SEL;
+	gswip_tag[3] = BIT(dp->index + GSWIP_TX_PORT_MAP_SHIFT) & GSWIP_TX_PORT_MAP_MASK;
+	gswip_tag[3] |= GSWIP_TX_DPID_EN;
+
+	return skb;
+}
+
+static struct sk_buff *gswip_tag_rcv(struct sk_buff *skb,
+				     struct net_device *dev,
+				     struct packet_type *pt)
+{
+	int port;
+	u8 *gswip_tag;
+
+	if (unlikely(!pskb_may_pull(skb, GSWIP_RX_HEADER_LEN)))
+		return NULL;
+
+	gswip_tag = skb->data - ETH_HLEN;
+
+	/* Get source port information */
+	port = (gswip_tag[7] & GSWIP_RX_SPPID_MASK) >> GSWIP_RX_SPPID_SHIFT;
+	skb->dev = dsa_master_find_slave(dev, 0, port);
+	if (!skb->dev)
+		return NULL;
+
+	/* remove GSWIP tag */
+	skb_pull_rcsum(skb, GSWIP_RX_HEADER_LEN);
+
+	return skb;
+}
+
+const struct dsa_device_ops gswip_netdev_ops = {
+	.xmit = gswip_tag_xmit,
+	.rcv = gswip_tag_rcv,
+};