diff --git a/drivers/net/dsa/Kconfig b/drivers/net/dsa/Kconfig
index d0024cb30a7ba3f722e6bb846bed92f3a6262880..468b3c4273c5bb709f780932244737b86385ea77 100644
--- a/drivers/net/dsa/Kconfig
+++ b/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
diff --git a/drivers/net/dsa/rtl8366rb.c b/drivers/net/dsa/rtl8366rb.c
index fd1977590cb4b4f4dc174bef357c63e716b0dc82..48f1ff74679993eafae1af16fe2e8a928290a15a 100644
--- a/drivers/net/dsa/rtl8366rb.c
+++ b/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,
diff --git a/include/net/dsa.h b/include/net/dsa.h
index 4046ccd1945d5230b015b2f39cc2c481e5ed902e..b28c95c767621e64a1cc09571f3ace5c8e2ee868 100644
--- a/include/net/dsa.h
+++ b/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;
diff --git a/net/dsa/Kconfig b/net/dsa/Kconfig
index d5bc6ac599ef013cee05dbe2e2b97674fe09142d..1f9b9b11008cbab5c6822192ce84be2febe58e04 100644
--- a/net/dsa/Kconfig
+++ b/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
diff --git a/net/dsa/Makefile b/net/dsa/Makefile
index 108486cfdeefe57a101c01f2c3bb6c48831fb33a..4f47b2025ff5d60d2c8086fd14e2aabec19a182a 100644
--- a/net/dsa/Makefile
+++ b/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
diff --git a/net/dsa/tag_rtl4_a.c b/net/dsa/tag_rtl4_a.c
new file mode 100644
index 0000000000000000000000000000000000000000..7b63010fa87ba4afdfd2616399bd23e08f0f1513
--- /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);