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, 100 insertions, 0 deletions

diff --git a/target/linux/generic/backport-5.4/758-v5.8-net-dsa-rtl8366rb-Support-the-CPU-DSA-tag.patch b/target/linux/generic/backport-5.4/758-v5.8-net-dsa-rtl8366rb-Support-the-CPU-DSA-tag.patch
new file mode 100644
index 0000000000..b68c033bbe
--- /dev/null
+++ b/target/linux/generic/backport-5.4/758-v5.8-net-dsa-rtl8366rb-Support-the-CPU-DSA-tag.patch
@@ -0,0 +1,100 @@
+From c633ba43b7a9c2bfdb992ffd198d4c661520466f Mon Sep 17 00:00:00 2001
+From: Linus Walleij <linus.walleij@linaro.org>
+Date: Wed, 8 Jul 2020 14:25:37 +0200
+Subject: [PATCH 3/5] net: dsa: rtl8366rb: Support the CPU DSA tag
+
+This activates the support to use the CPU tag to properly
+direct ingress traffic to the right port.
+
+Bit 15 in register RTL8368RB_CPU_CTRL_REG can be set to
+1 to disable the insertion of the CPU tag which is what
+the code currently does. The bit 15 define calls this
+setting RTL8368RB_CPU_INSTAG which is confusing since the
+inverse meaning is implied: programmers may think that
+setting this bit to 1 will *enable* inserting the tag
+rather than disabling it, so rename this setting in
+bit 15 to RTL8368RB_CPU_NO_TAG which is more to the
+point.
+
+After this e.g. ping works out-of-the-box with the
+RTL8366RB.
+
+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>
+---
+ drivers/net/dsa/Kconfig     |  1 +
+ drivers/net/dsa/rtl8366rb.c | 31 ++++++++-----------------------
+ 2 files changed, 9 insertions(+), 23 deletions(-)
+
+--- a/drivers/net/dsa/Kconfig
++++ b/drivers/net/dsa/Kconfig
+@@ -66,6 +66,7 @@ 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
+--- 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_sw
+ 	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;
+ 
+@@ -966,21 +964,8 @@ static int rtl8366rb_setup(struct dsa_sw
+ static enum dsa_tag_protocol rtl8366_get_tag_protocol(struct dsa_switch *ds,
+ 						      int port)
+ {
+-	/* 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,