Merge branch 'RTL8366RB-tagging-support'

Linus Walleij says:

====================
RTL8366RB tagging support

This patch set adds DSA tagging support to the RTL8366RB
DSA driver.

There is a minor performance improvement in the tag parser
compared to the previous patch set and the review tags
have been collected.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/Kconfig

@@ -70,6 +70,7 @@ config NET_DSA_QCA8K
 config NET_DSA_REALTEK_SMI
 	tristate "Realtek SMI Ethernet switch family support"
 	depends on NET_DSA
+	select NET_DSA_TAG_RTL4_A
 	select FIXED_PHY
 	select IRQ_DOMAIN
 	select REALTEK_PHY

drivers/net/dsa/rtl8366rb.c

@@ -109,8 +109,8 @@
 /* CPU port control reg */
 #define RTL8368RB_CPU_CTRL_REG		0x0061
 #define RTL8368RB_CPU_PORTS_MSK		0x00FF
-/* Enables inserting custom tag length/type 0x8899 */
-#define RTL8368RB_CPU_INSTAG		BIT(15)
+/* Disables inserting custom tag length/type 0x8899 */
+#define RTL8368RB_CPU_NO_TAG		BIT(15)
 
 #define RTL8366RB_SMAR0			0x0070 /* bits 0..15 */
 #define RTL8366RB_SMAR1			0x0071 /* bits 16..31 */
@@ -844,16 +844,14 @@ static int rtl8366rb_setup(struct dsa_switch *ds)
 	if (ret)
 		return ret;
 
-	/* Enable CPU port and enable inserting CPU tag
+	/* Enable CPU port with custom DSA tag 8899.
 	 *
-	 * Disabling RTL8368RB_CPU_INSTAG here will change the behaviour
-	 * of the switch totally and it will start talking Realtek RRCP
-	 * internally. It is probably possible to experiment with this,
-	 * but then the kernel needs to understand and handle RRCP first.
+	 * If you set RTL8368RB_CPU_NO_TAG (bit 15) in this registers
+	 * the custom tag is turned off.
 	 */
 	ret = regmap_update_bits(smi->map, RTL8368RB_CPU_CTRL_REG,
 				 0xFFFF,
-				 RTL8368RB_CPU_INSTAG | BIT(smi->cpu_port));
+				 BIT(smi->cpu_port));
 	if (ret)
 		return ret;
 
@@ -967,21 +965,8 @@ static enum dsa_tag_protocol rtl8366_get_tag_protocol(struct dsa_switch *ds,
 						      int port,
 						      enum dsa_tag_protocol mp)
 {
-	/* For now, the RTL switches are handled without any custom tags.
-	 *
-	 * It is possible to turn on "custom tags" by removing the
-	 * RTL8368RB_CPU_INSTAG flag when enabling the port but what it
-	 * does is unfamiliar to DSA: ethernet frames of type 8899, the Realtek
-	 * Remote Control Protocol (RRCP) start to appear on the CPU port of
-	 * the device. So this is not the ordinary few extra bytes in the
-	 * frame. Instead it appears that the switch starts to talk Realtek
-	 * RRCP internally which means a pretty complex RRCP implementation
-	 * decoding and responding the RRCP protocol is needed to exploit this.
-	 *
-	 * The OpenRRCP project (dormant since 2009) have reverse-egineered
-	 * parts of the protocol.
-	 */
-	return DSA_TAG_PROTO_NONE;
+	/* This switch uses the 4 byte protocol A Realtek DSA tag */
+	return DSA_TAG_PROTO_RTL4_A;
 }
 
 static void rtl8366rb_adjust_link(struct dsa_switch *ds, int port,

include/net/dsa.h

@@ -44,6 +44,7 @@ struct phylink_link_state;
 #define DSA_TAG_PROTO_KSZ8795_VALUE		14
 #define DSA_TAG_PROTO_OCELOT_VALUE		15
 #define DSA_TAG_PROTO_AR9331_VALUE		16
+#define DSA_TAG_PROTO_RTL4_A_VALUE		17
 
 enum dsa_tag_protocol {
 	DSA_TAG_PROTO_NONE		= DSA_TAG_PROTO_NONE_VALUE,
@@ -63,6 +64,7 @@ enum dsa_tag_protocol {
 	DSA_TAG_PROTO_KSZ8795		= DSA_TAG_PROTO_KSZ8795_VALUE,
 	DSA_TAG_PROTO_OCELOT		= DSA_TAG_PROTO_OCELOT_VALUE,
 	DSA_TAG_PROTO_AR9331		= DSA_TAG_PROTO_AR9331_VALUE,
+	DSA_TAG_PROTO_RTL4_A		= DSA_TAG_PROTO_RTL4_A_VALUE,
 };
 
 struct packet_type;

net/dsa/Kconfig

@@ -86,6 +86,13 @@ config NET_DSA_TAG_KSZ
 	  Say Y if you want to enable support for tagging frames for the
 	  Microchip 8795/9477/9893 families of switches.
 
+config NET_DSA_TAG_RTL4_A
+	tristate "Tag driver for Realtek 4 byte protocol A tags"
+	help
+	  Say Y or M if you want to enable support for tagging frames for the
+	  Realtek switches with 4 byte protocol A tags, sich as found in
+	  the Realtek RTL8366RB.
+
 config NET_DSA_TAG_OCELOT
 	tristate "Tag driver for Ocelot family of switches"
 	select PACKING

net/dsa/Makefile

@@ -11,6 +11,7 @@ obj-$(CONFIG_NET_DSA_TAG_DSA) += tag_dsa.o
 obj-$(CONFIG_NET_DSA_TAG_EDSA) += tag_edsa.o
 obj-$(CONFIG_NET_DSA_TAG_GSWIP) += tag_gswip.o
 obj-$(CONFIG_NET_DSA_TAG_KSZ) += tag_ksz.o
+obj-$(CONFIG_NET_DSA_TAG_RTL4_A) += tag_rtl4_a.o
 obj-$(CONFIG_NET_DSA_TAG_LAN9303) += tag_lan9303.o
 obj-$(CONFIG_NET_DSA_TAG_MTK) += tag_mtk.o
 obj-$(CONFIG_NET_DSA_TAG_OCELOT) += tag_ocelot.o

net/dsa/tag_rtl4_a.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Handler for Realtek 4 byte DSA switch tags
+ * Currently only supports protocol "A" found in RTL8366RB
+ * Copyright (c) 2020 Linus Walleij <linus.walleij@linaro.org>
+ *
+ * This "proprietary tag" header looks like so:
+ *
+ * -------------------------------------------------
+ * | MAC DA | MAC SA | 0x8899 | 2 bytes tag | Type |
+ * -------------------------------------------------
+ *
+ * The 2 bytes tag form a 16 bit big endian word. The exact
+ * meaning has been guessed from packet dumps from ingress
+ * frames, as no working egress traffic has been available
+ * we do not know the format of the egress tags or if they
+ * are even supported.
+ */
+
+#include <linux/etherdevice.h>
+#include <linux/bits.h>
+
+#include "dsa_priv.h"
+
+#define RTL4_A_HDR_LEN		4
+#define RTL4_A_ETHERTYPE	0x8899
+#define RTL4_A_PROTOCOL_SHIFT	12
+/*
+ * 0x1 = Realtek Remote Control protocol (RRCP)
+ * 0x2/0x3 seems to be used for loopback testing
+ * 0x9 = RTL8306 DSA protocol
+ * 0xa = RTL8366RB DSA protocol
+ */
+#define RTL4_A_PROTOCOL_RTL8366RB	0xa
+
+static struct sk_buff *rtl4a_tag_xmit(struct sk_buff *skb,
+				      struct net_device *dev)
+{
+	/*
+	 * Just let it pass thru, we don't know if it is possible
+	 * to tag a frame with the 0x8899 ethertype and direct it
+	 * to a specific port, all attempts at reverse-engineering have
+	 * ended up with the frames getting dropped.
+	 *
+	 * The VLAN set-up needs to restrict the frames to the right port.
+	 *
+	 * If you have documentation on the tagging format for RTL8366RB
+	 * (tag type A) then please contribute.
+	 */
+	return skb;
+}
+
+static struct sk_buff *rtl4a_tag_rcv(struct sk_buff *skb,
+				     struct net_device *dev,
+				     struct packet_type *pt)
+{
+	u16 protport;
+	__be16 *p;
+	u16 etype;
+	u8 *tag;
+	u8 prot;
+	u8 port;
+
+	if (unlikely(!pskb_may_pull(skb, RTL4_A_HDR_LEN)))
+		return NULL;
+
+	/* The RTL4 header has its own custom Ethertype 0x8899 and that
+	 * starts right at the beginning of the packet, after the src
+	 * ethernet addr. Apparantly skb->data always points 2 bytes in,
+	 * behind the Ethertype.
+	 */
+	tag = skb->data - 2;
+	p = (__be16 *)tag;
+	etype = ntohs(*p);
+	if (etype != RTL4_A_ETHERTYPE) {
+		/* Not custom, just pass through */
+		netdev_dbg(dev, "non-realtek ethertype 0x%04x\n", etype);
+		return skb;
+	}
+	p = (__be16 *)(tag + 2);
+	protport = ntohs(*p);
+	/* The 4 upper bits are the protocol */
+	prot = (protport >> RTL4_A_PROTOCOL_SHIFT) & 0x0f;
+	if (prot != RTL4_A_PROTOCOL_RTL8366RB) {
+		netdev_err(dev, "unknown realtek protocol 0x%01x\n", prot);
+		return NULL;
+	}
+	port = protport & 0xff;
+
+	skb->dev = dsa_master_find_slave(dev, 0, port);
+	if (!skb->dev) {
+		netdev_dbg(dev, "could not find slave for port %d\n", port);
+		return NULL;
+	}
+
+	/* Remove RTL4 tag and recalculate checksum */
+	skb_pull_rcsum(skb, RTL4_A_HDR_LEN);
+
+	/* Move ethernet DA and SA in front of the data */
+	memmove(skb->data - ETH_HLEN,
+		skb->data - ETH_HLEN - RTL4_A_HDR_LEN,
+		2 * ETH_ALEN);
+
+	skb->offload_fwd_mark = 1;
+
+	return skb;
+}
+
+static int rtl4a_tag_flow_dissect(const struct sk_buff *skb, __be16 *proto,
+				  int *offset)
+{
+	*offset = RTL4_A_HDR_LEN;
+	/* Skip past the tag and fetch the encapsulated Ethertype */
+	*proto = ((__be16 *)skb->data)[1];
+
+	return 0;
+}
+
+static const struct dsa_device_ops rtl4a_netdev_ops = {
+	.name	= "rtl4a",
+	.proto	= DSA_TAG_PROTO_RTL4_A,
+	.xmit	= rtl4a_tag_xmit,
+	.rcv	= rtl4a_tag_rcv,
+	.flow_dissect = rtl4a_tag_flow_dissect,
+	.overhead = RTL4_A_HDR_LEN,
+};
+module_dsa_tag_driver(rtl4a_netdev_ops);
+
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_RTL4_A);