ramips: add support for UniElec U7621-06

ramips: add support for UniElec U7621-06

UniElec U7621-06 is a router platform board based on MediaTek MT7621AT.
The device has the following specifications:

- MT7621AT (880 MHz)
- 256/512 MB of RAM (DDR3)
- 8/16/32/64 MB of FLASH (SPI NOR)
- 5x 1 Gbps Ethernet (MT7621 built-in switch)
- 1x ASMedia ASM1061 (for mSATA and SATA)
- 2x miniPCIe slots (PCIe bus only)
- 1x mSATA slot (with USB 2.0 bus for modem)
- 1x SATA
- 1x miniSIM slot
- 1x microSD slot
- 1x USB 3.0
- 12x LEDs (3 GPIO-controlled)
- 1x reset button
- 1x UART header (4-pins)
- 1x GPIO header (30-pins)
- 1x FPC connector for LEDs (20-pin, 0.5 mm pitch)
- 1x DC jack for main power (12 V)

The following has been tested and is working:

- Ethernet switch
- miniPCIe slots (tested with Wi-Fi cards)
- mSATA slot (tested with modem and mSATA drive)
- miniSIM slot
- sysupgrade
- reset button
- microSD slot

Installation:

This board might come with a different firmware versions (MediaTek SDK,
PandoraBox, Padavan, etc.). If your board comes with PandoraBox, you can
install LEDE using sysupgrade. Just SSH to the router and perform forced
sysupgrade (due to a board name mismatch). The default IP of this board
should be: 192.168.1.1 and username/password: root/admin. In case of a
different firmware, you can use web based recovery described below.

Use the following command to perform the sysupgrade (for the 256MB
RAM/16MB flash version):

sysupgrade -n -F lede-ramips-mt7621-u7621-06-256M-16M-squashfs-sysupgrade.bin

Recovery:

This board contains a Chinese, closed-source bootloader called Breed
(Boot and Recovery Environment for Embedded Devices). Breed supports web
recovery and to enter it, you keep the reset button pressed for around
5 seconds during boot. Your machine will be assigned an IP through DHCP
and the router will use IP address 192.168.1.1. The recovery website is
in Chinese, but is easy to use. Click on the second item in the list to
access the recovery page, then the second item on the next page is where
you select the firmware. In order to start the recovery, you click the
button at the bottom.

LEDs list (top row, left to right):

- LED_WWAN# (connected with pin 42 in LTE/mSATA slot)
- Power (connected directly to 3V3)
- CTS2_N (GPIO10, configured as "status" LED)
- TXD2 (GPIO11, configured as "led4", without default trigger)
- RXD2 (GPIO12, configured as "led5", without default trigger)
- LED_WLAN# (connected with pin 44 in wifi0 slot)

LEDs list (bottom row, left to right):

- ESW_P0_LED_0
- ESW_P1_LED_0
- ESW_P2_LED_0
- ESW_P3_LED_0
- ESW_P4_LED_0
- LED_WLAN# (connected with pin 44 in wifi1 slot)

Other notes:

1. The board is available with different amounts of RAM and flash. We
have only added support for the 256/16 MB configuration, as that seems
to be the default. However, all the required infrastructure is in place
for making support for the other configurations easy.

2. The manufacturer offers five different wireless cards with MediaTek
chipsets, based on MT76x2, MT7603 and MT7615. Images of the board all
show that the miniPCIe slots are dedicated to specific Wi-Fi cards.
However, the slots are generic.

3. All boards we got access to had the same EEPROM content. The default
firmware reads the Ethernet MAC from offset 0xe000 in factory partition.
This offset only contains 0xffs, so a random MAC will be generated on
every boot of the router. There is a valid MAC stored at offset 0xe006
and this MAC is shown as the WAN MAC in the bootloader. However, it is
the same on all boards we have checked. Based on information provided
by the vendor, all boards sold in small quantities are considered more
as samples for development purposes.

Signed-off-by: Piotr Dymacz <pepe2k@gmail.com>
Signed-off-by: Kristian Evensen <kristian.evensen@gmail.com>