kernel: backport RTL8366RB patches

These upstream patches makes the RTL8366RB DSA switch work
properly with OpenWrt, the D-Link DIR-685 gets network and
can be used as a router, and the same should be applicable
for any other device that want to enable the RTL8366RB
through Device Tree.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 232 insertions, 0 deletions

diff --git a/target/linux/generic/backport-5.4/757-v5.8-net-dsa-tag_rtl4_a-Implement-Realtek-4-byte-A-tag.patch b/target/linux/generic/backport-5.4/757-v5.8-net-dsa-tag_rtl4_a-Implement-Realtek-4-byte-A-tag.patch
new file mode 100644
index 0000000000..70d7000ba1
--- /dev/null
+++ b/target/linux/generic/backport-5.4/757-v5.8-net-dsa-tag_rtl4_a-Implement-Realtek-4-byte-A-tag.patch
@@ -0,0 +1,232 @@
+From 078ced30af696b52a450a016a16eb47499d68117 Mon Sep 17 00:00:00 2001
+From: Linus Walleij <linus.walleij@linaro.org>
+Date: Wed, 8 Jul 2020 14:25:36 +0200
+Subject: [PATCH 2/5] net: dsa: tag_rtl4_a: Implement Realtek 4 byte A tag
+
+This implements the known parts of the Realtek 4 byte
+tag protocol version 0xA, as found in the RTL8366RB
+DSA switch.
+
+It is designated as protocol version 0xA as a
+different Realtek 4 byte tag format with protocol
+version 0x9 is known to exist in the Realtek RTL8306
+chips.
+
+The tag and switch chip lacks public documentation, so
+the tag format has been reverse-engineered from
+packet dumps. As only ingress traffic has been available
+for analysis an egress tag has not been possible to
+develop (even using educated guesses about bit fields)
+so this is as far as it gets. It is not known if the
+switch even supports egress tagging.
+
+Excessive attempts to figure out the egress tag format
+was made. When nothing else worked, I just tried all bit
+combinations with 0xannp where a is protocol and p is
+port. I looped through all values several times trying
+to get a response from ping, without any positive
+result.
+
+Using just these ingress tags however, the switch
+functionality is vastly improved and the packets find
+their way into the destination port without any
+tricky VLAN configuration. On the D-Link DIR-685 the
+LAN ports now come up and respond to ping without
+any command line configuration so this is a real
+improvement for users.
+
+Egress packets need to be restricted to the proper
+target ports using VLAN, which the RTL8366RB DSA
+switch driver already sets up.
+
+Cc: DENG Qingfang <dqfext@gmail.com>
+Cc: Mauri Sandberg <sandberg@mailfence.com>
+Reviewed-by: Andrew Lunn <andrew@lunn.ch>
+Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
+Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+---
+ include/net/dsa.h    |   2 +
+ net/dsa/Kconfig      |   7 +++
+ net/dsa/Makefile     |   1 +
+ net/dsa/tag_rtl4_a.c | 130 +++++++++++++++++++++++++++++++++++++++++++
+ 4 files changed, 140 insertions(+)
+ create mode 100644 net/dsa/tag_rtl4_a.c
+
+--- a/include/net/dsa.h
++++ b/include/net/dsa.h
+@@ -42,6 +42,7 @@ struct phylink_link_state;
+ #define DSA_TAG_PROTO_8021Q_VALUE		12
+ #define DSA_TAG_PROTO_SJA1105_VALUE		13
+ #define DSA_TAG_PROTO_KSZ8795_VALUE		14
++#define DSA_TAG_PROTO_RTL4_A_VALUE		17
+ 
+ enum dsa_tag_protocol {
+ 	DSA_TAG_PROTO_NONE		= DSA_TAG_PROTO_NONE_VALUE,
+@@ -59,6 +60,7 @@ enum dsa_tag_protocol {
+ 	DSA_TAG_PROTO_8021Q		= DSA_TAG_PROTO_8021Q_VALUE,
+ 	DSA_TAG_PROTO_SJA1105		= DSA_TAG_PROTO_SJA1105_VALUE,
+ 	DSA_TAG_PROTO_KSZ8795		= DSA_TAG_PROTO_KSZ8795_VALUE,
++	DSA_TAG_PROTO_RTL4_A		= DSA_TAG_PROTO_RTL4_A_VALUE,
+ };
+ 
+ struct packet_type;
+--- a/net/dsa/Kconfig
++++ b/net/dsa/Kconfig
+@@ -80,6 +80,13 @@ 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_QCA
+ 	tristate "Tag driver for Qualcomm Atheros QCA8K switches"
+ 	help
+--- a/net/dsa/Makefile
++++ b/net/dsa/Makefile
+@@ -10,6 +10,7 @@ obj-$(CONFIG_NET_DSA_TAG_DSA) += tag_dsa
+ obj-$(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_QCA) += tag_qca.o
+--- /dev/null
++++ b/net/dsa/tag_rtl4_a.c
+@@ -0,0 +1,130 @@
++// 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);