ramips: add support for TP-Link Archer C20 v5

TP-Link Archer C20 v5 is a router with 5-port FE switch and
non-detachable antennas. It's based on MediaTek MT7628N+MT7610EN.

Specification:
- MediaTek MT7628N/N (580 Mhz)
- 64 MB of RAM
- 8 MB of FLASH
- 2T2R 2.4 GHz and 1T1R 5 GHz
- 5x 10/100 Mbps Ethernet
- 3x external, non-detachable antennas
- UART (J1) header on PCB (115200 8n1)
- 7x LED (GPIO-controlled*), 2x button, power input switch

* WAN LED in this devices is a dual-color, dual-leads type which isn't
  (fully) supported by gpio-leds driver. This type of LED requires both
  GPIOs state change at the same time to select color or turn it off.
  For now, we support/use only the green part of the LED.

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 Website 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 TP-Link MediaTek device with a split-uboot feature design like
a TP-Link Archer C50 v4. 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 / Archer C50v4. 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: Maxim Anisimov <maxim.anisimov.ua@gmail.com>
[adjust some node names for LEDs in DTS]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

2 files changed, 4 insertions, 1 deletions

diff --git a/target/linux/ramips/mt76x8/base-files/etc/board.d/01_leds b/target/linux/ramips/mt76x8/base-files/etc/board.d/01_leds
index 06b78eb195..79f45ba545 100755
--- a/target/linux/ramips/mt76x8/base-files/etc/board.d/01_leds
+++ b/target/linux/ramips/mt76x8/base-files/etc/board.d/01_leds
@@ -52,7 +52,8 @@ tama,w06)
 	ucidef_set_led_netdev "wan" "WAN" "$boardname:green:wan" "eth0"
 	ucidef_set_led_wlan "wlan" "WLAN" "$boardname:green:wlan" "phy0tpt"
 	;;
-tplink,archer-c20-v4)
+tplink,archer-c20-v4|\
+tplink,archer-c20-v5)
 	ucidef_set_led_switch "lan" "lan" "$boardname:green:lan" "switch0" "0x1e"
 	ucidef_set_led_switch "wan" "wan" "$boardname:green:wan" "switch0" "0x01"
 	;;
diff --git a/target/linux/ramips/mt76x8/base-files/etc/board.d/02_network b/target/linux/ramips/mt76x8/base-files/etc/board.d/02_network
index a733353f71..646e29235c 100755
--- a/target/linux/ramips/mt76x8/base-files/etc/board.d/02_network
+++ b/target/linux/ramips/mt76x8/base-files/etc/board.d/02_network
@@ -40,6 +40,7 @@ ramips_setup_interfaces()
 	hiwifi,hc5861b|\
 	skylab,skw92a|\
 	tplink,archer-c20-v4|\
+	tplink,archer-c20-v5|\
 	tplink,archer-c50-v3|\
 	tplink,archer-c50-v4|\
 	tplink,tl-mr3420-v5|\
@@ -191,6 +192,7 @@ ramips_setup_macs()
 	tplink,tl-wr842n-v5)
 		wan_mac=$(macaddr_add "$(mtd_get_mac_binary factory 0xf100)" 1)
 		;;
+	tplink,archer-c20-v5|\
 	tplink,archer-c50-v4)
 		wan_mac=$(macaddr_add "$(mtd_get_mac_binary rom 0xf100)" 1)
 		;;