ramips: add support for Archer C50 v4

This adds support for the TP-Link Archer C50 v4.
It uses the same hardware as the v3 variant, sharing the same FCC-ID.

CPU:   MediaTek MT7628 (580MHz)
RAM:   64M DDR2
FLASH: 8M SPI
WiFi:  2.4GHz 2x2 MT7628 b/g/n integrated
WiFI:  5GHz 2x2 MT7612 a/n/ac
ETH:   1x WAN 4x LAN
LED:   Power, WiFi2, WiFi5, LAN, WAN, WPS
BTN:   WPS/WiFi, RESET
UART:  Near ETH ports, 115200 8n1, TP-Link pinout

Create Factory image
--------------------
As all installation methods require a U-Boot to be integrated into the
Image (and we do not ship one with the image) we are not able to create
an image in the OpenWRT build-process.

Download a TP-Link image from their Wesite and a OpenWRT sysupgrade
image for the device and build yourself a factory image like following:

TP-Link image:             tpl.bin
OpenWRT sysupgrade image:  owrt.bin

 > dd if=tpl.bin of=boot.bin bs=131584 count=1
 > cat owrt.bin >> boot.bin

Installing via Web-UI
---------------------
Upload the boot.bin via TP-Links firmware upgrade tool in the
web-interface.

Installing via Recovery
-----------------------
Activate Web-Recovery by beginning the upgrade Process with a
Firmware-Image from TP-Link. After starting the Firmware Upgrade,
wait ~3 seconds (When update status is switching to 0%), then
disconnect the power supply from the device. Upgrade flag (which
activates Web-Recovery) is written before the OS-image is touched and
removed after write is succesfull, so this procedure should be safe.

Plug the power back in. It will come up in Recovery-Mode on 192.168.0.1.
When active, all LEDs but the WPS LED are off.
Remeber to assign yourself a static IP-address as DHCP is not active in
this mode.

The boot.bin can now be uploaded and flashed using the web-recovery.

Installing via TFTP
-------------------
Prepare an image like following (Filenames from factory image steps
apply here)

 > dd if=/dev/zero of=tp_recovery.bin bs=196608 count=1
 > dd if=tpl.bin of=tmp.bin bs=131584 count=1
 > dd if=tmp.bin of=boot.bin bs=512 skip=1
 > cat boot.bin >> tp_recovery.bin
 > cat owrt.bin >> tp_recovery.bin

Place tp_recovery.bin in root directory of TFTP server and listen on
192.168.0.66/24.

Connect router LAN ports with your computer and power up the router
while pressing the reset button. The router will download the image via
tftp and after ~1 Minute reboot into OpenWRT.

U-Boot CLI
----------
U-Boot CLI can be activated by holding down '4' on bootup.

Dual U-Boot
-----------
This is the first TP-Link MediaTek device to feature a split-uboot
design. The first (factory-uboot) provides recovery via TFTP and HTTP,
jumping straight into the second (firmware-uboot) if no recovery needs
to be performed. The firmware-uboot unpacks and executed the kernel.

Web-Recovery
------------
TP-Link integrated a new Web-Recovery like the one on the Archer C7v4 /
TL-WR1043v5. Stock-firmware sets a flag in the "romfile" partition
before beginning to write and removes it afterwards. If the router boots
with this flag set, bootloader will automatically start Web-recovery and
listens on 192.168.0.1. This way, the vendor-firmware or an OpenWRT
factory image can be written.

By doing the same while performing sysupgrade, we can take advantage of
the Web-recovery in OpenWRT.

It is important to note that Web-Recovery is only based on this flag. It
can't detect e.g. a crashing kernel or other means. Once activated it
won't boot the OS before a recovery action (either via TFTP or HTTP) is
performed. This recovery-mode is indicated by an illuminated WPS-LED on
boot.

Signed-off-by: David Bauer <mail@david-bauer.net>

2 files changed, 189 insertions, 0 deletions

diff --git a/target/linux/ramips/dts/ArcherC50V4.dts b/target/linux/ramips/dts/ArcherC50V4.dts
new file mode 100644
index 0000000000..37f388620e
--- /dev/null
+++ b/target/linux/ramips/dts/ArcherC50V4.dts
@@ -0,0 +1,99 @@
+// SPDX-License-Identifier: GPL-2.0-or-later OR MIT
+/dts-v1/;
+
+#include "TPLINK-8M-SPLIT-UBOOT.dtsi"
+
+#include <dt-bindings/gpio/gpio.h>
+#include <dt-bindings/input/input.h>
+
+/ {
+	compatible = "tplink,c50-v4", "mediatek,mt7628an-soc";
+	model = "TP-Link Archer C50 v4";
+
+	aliases {
+		led-boot = &led_power;
+		led-failsafe = &led_power;
+		led-running = &led_power;
+		led-upgrade = &led_power;
+	};
+
+	keys {
+		compatible = "gpio-keys-polled";
+		poll-interval = <20>;
+
+		reset {
+			label = "reset";
+			gpios = <&gpio1 6 GPIO_ACTIVE_LOW>;
+			linux,code = <KEY_RESTART>;
+		};
+
+		rfkill {
+			label = "rfkill";
+			gpios = <&gpio0 5 GPIO_ACTIVE_LOW>;
+			linux,code = <KEY_RFKILL>;
+		};
+	};
+
+	leds {
+		compatible = "gpio-leds";
+
+		led_power: power {
+			label = "c50-v4:green:power";
+			gpios = <&gpio0 11 GPIO_ACTIVE_LOW>;
+		};
+
+		wlan2 {
+			label = "c50-v4:green:wlan2g";
+			gpios = <&gpio1 12 GPIO_ACTIVE_LOW>;
+		};
+
+		wlan5 {
+			label = "c50-v4:green:wlan5g";
+			gpios = <&gpio1 10 GPIO_ACTIVE_LOW>;
+		};
+
+		lan {
+			label = "c50-v4:green:lan";
+			gpios = <&gpio1 9 GPIO_ACTIVE_LOW>;
+		};
+
+		wan {
+			label = "c50-v4:green:wan";
+			gpios = <&gpio1 7 GPIO_ACTIVE_LOW>;
+		};
+
+		wan_orange {
+			label = "c50-v4:orange:wan";
+			gpios = <&gpio1 8 GPIO_ACTIVE_LOW>;
+		};
+
+		wps {
+			label = "c50-v4:green:wps";
+			gpios = <&gpio1 11 GPIO_ACTIVE_LOW>;
+		};
+	};
+};
+
+&pinctrl {
+	state_default: pinctrl0 {
+		gpio {
+			ralink,group = "i2c", "p0led_an", "p1led_an", "p2led_an",
+				       "p3led_an", "p4led_an", "wdt", "wled_an";
+			ralink,function = "gpio";
+		};
+	};
+};
+
+&pcie {
+	status = "okay";
+};
+
+&pcie0 {
+	wifi@0,0 {
+		reg = <0x0000 0 0 0 0>;
+		mediatek,mtd-eeprom = <&radio 0x8000>;
+		ieee80211-freq-limit = <5000000 6000000>;
+		mtd-mac-address = <&rom 0xf100>;
+		mtd-mac-address-increment = <(-1)>;
+	};
+};
diff --git a/target/linux/ramips/dts/TPLINK-8M-SPLIT-UBOOT.dtsi b/target/linux/ramips/dts/TPLINK-8M-SPLIT-UBOOT.dtsi
new file mode 100644
index 0000000000..539f476dce
--- /dev/null
+++ b/target/linux/ramips/dts/TPLINK-8M-SPLIT-UBOOT.dtsi
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0-or-later OR MIT
+#include "mt7628an.dtsi"
+
+/ {
+	chosen {
+		bootargs = "console=ttyS0,115200";
+	};
+
+	memory@0 {
+		device_type = "memory";
+		reg = <0x0 0x4000000>;
+	};
+};
+
+&spi0 {
+	status = "okay";
+
+	flash@0 {
+		compatible = "jedec,spi-nor";
+		reg = <0>;
+		spi-max-frequency = <10000000>;
+		m25p,chunked-io = <32>;
+
+		partitions {
+			compatible = "fixed-partitions";
+			#address-cells = <1>;
+			#size-cells = <1>;
+
+			partition@0 {
+				label = "factory-uboot";
+				reg = <0x0 0x30000>;
+				read-only;
+			};
+
+			partition@30000 {
+				label = "boot";
+				reg = <0x30000 0x20000>;
+				read-only;
+			};
+
+			partition@50000 {
+				compatible = "tplink,firmware";
+				label = "firmware";
+				reg = <0x50000 0x770000>;
+			};
+
+			partition@7c0000 {
+				label = "config";
+				reg = <0x7c0000 0x10000>;
+				read-only;
+			};
+
+			rom: partition@7d0000 {
+				label = "rom";
+				reg = <0x7d0000 0x10000>;
+				read-only;
+			};
+
+			partition@7e0000 {
+				label = "romfile";
+				reg = <0x7e0000 0x10000>;
+			};
+
+			radio: partition@7f0000 {
+				label = "radio";
+				reg = <0x7f0000 0x10000>;
+				read-only;
+			};
+		};
+	};
+};
+
+&ehci {
+	status = "disabled";
+};
+
+&ohci {
+	status = "disabled";
+};
+
+&wmac {
+	status = "okay";
+	mtd-mac-address = <&rom 0xf100>;
+	mediatek,mtd-eeprom = <&radio 0x0>;
+};
+
+&ethernet {
+	mtd-mac-address = <&rom 0xf100>;
+	mediatek,portmap = "llllw";
+};