econet: Add new target TP-Link Archer VR1200v (v2)

The TP-Link Archer VR1200v (v2) is a low end DSL modem based on the
EcoNet EN751221 processor platform.

While it does have an unlocked bootloader, the factory upgrade feature
requires a cryptographic signature so flashing from the web UI is not
feasible.

The Archer VR1200v (v2) uses a dual-image layout. I have chosen to reuse
this to support dual-boot between OpenWRT and the factory firmware.

Flashing instructions (from bootloader):

Build and then locate the squashfs-sysupgrade.bin image file
Get the length of that file in hex: printf '%X\n' "$(stat -c%s the-file-squashfs-sysupgrade.bin)"
Connect to device with xmodem capability, e.g. picocom --send-cmd lsx -vv -b 115200 /dev/ttyUSB0
Switch device on and press a key within 3 seconds, you should get to a `bldr>` prompt
Type: xmdm 80020000 <file length hex>
Quickly start xmodem and send the file, in picocom that is ctrl+a ctrl+s <paste-the-file-name> enter If the transfer fails to start, wait 30 seconds to a minute for the bootloader prompt to return and then try the command again.
Once the transfer has completed successfully, type the following flash 80000 80020000 <file length hex>
Type `re` or simply restart the device to boot into OpenWRT

Signed-off-by: Caleb James DeLisle <cjd@cjdns.fr>
Link: https://github.com/openwrt/openwrt/pull/19021
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

target/linux/econet/dts/en751221_tplink_archer-vr1200v-v2.dts

@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+/dts-v1/;
+
+#include "en751221.dtsi"
+
+/ {
+	model = "TP-Link Archer VR1200v (v2)";
+	compatible = "tplink,archer-vr1200v-v2", "econet,en751221";
+
+	memory@0 {
+		device_type = "memory";
+		reg = <0x00000000 0x8000000>;
+	};
+
+	chosen {
+		stdout-path = "/serial@1fbf0000:115200";
+		linux,usable-memory-range = <0x00020000 0x07fe0000>;
+	};
+};
+
+&nand {
+	status = "okay";
+	econet,bmt;
+
+	partitions {
+		compatible = "fixed-partitions";
+		#address-cells = <1>;
+		#size-cells = <1>;
+
+		partition@0 {
+			label = "bootloader";
+			reg = <0x0 0x00080000>;
+			read-only;
+		};
+		partition@80000 {
+			label = "misc";
+			reg = <0x00080000 0x140000>;
+		};
+		partition@1c0200 {
+			label = "kernel";
+			reg = <0x001c0000 0x400000>;
+		};
+		partition@5c0000 {
+			label = "rootfs";
+			reg = <0x005c0000 0x1a40000>;
+			linux,rootfs;
+		};
+		partition@1c0000 {
+			label = "firmware";
+			reg = <0x001c0000 0x1e40000>;
+		};
+		partition@2000000 {
+			label = "firmware_factory";
+			reg = <0x2000000 0x1e40000>;
+		};
+		partition@3fe0000 {
+			label = "reserve";
+			reg = <0x3fe0000 0x20000>;
+		};
+		partition@4000000 {
+			label = "openwrt_ubi";
+			/* From the factory this is unallocated space, so it's ours for the taking.
+			 * We have up to 0x35e0000 of space, but we reserve 10 eraseblocks (1.25MB)
+			 * in case the BMT steals them from us.
+			 */
+			reg = <0x4000000 0x34a0000>;
+		};
+	};
+};

target/linux/econet/image/Makefile

@@ -30,4 +30,22 @@ define Device/smartfiber_xp8421-b
 endef
 TARGET_DEVICES += smartfiber_xp8421-b
 
+# NOTE: This will not work for upgrading from factory because it requires a cryptographic signature
+#       however, it it can be flashed, then it will boot correctly.
+define Device/tplink_archer-vr1200v-v2
+  DEVICE_VENDOR := TP-Link
+  DEVICE_MODEL := Archer vr1200v
+  DEVICE_VARIANT := v2
+  TPLINK_FLASHLAYOUT := 16Mmtk
+  TPLINK_HWID := 0x0b473502
+  TPLINK_HWREV := 0x0006007c
+  TPLINK_HWREVADD := 0x0
+  TPLINK_HVERSION := 3
+  DEVICE_DTS := en751221_tplink_archer-vr1200v-v2
+  IMAGES := sysupgrade.bin
+  IMAGE/sysupgrade.bin := append-kernel | lzma | pad-to 4193792 | append-rootfs | \
+    tplink-v2-header -R 0x400000
+endef
+TARGET_DEVICES += tplink_archer-vr1200v-v2
+
 $(eval $(call BuildImage))