ath79: add support for Senao Engenius ENS202EXT v1

ath79: add support for Senao Engenius ENS202EXT v1

Engenius ENS202EXT v1 is an outdoor wireless access point with 2 10/100 ports,
with built-in ethernet switch, detachable antennas and proprietery PoE.

FCC ID:	A8J-ENS202

Specification:

  - Qualcomm/Atheros AR9341 v1
  - 535/400/200/40 MHz          (CPU/DDR/AHB/REF)
  - 64 MB of RAM
  - 16 MB of FLASH              MX25L12835F(MI-10G)
  - UART (J1) header on PCB     (unpopulated)
  - 2x 10/100 Mbps Ethernet     (built-in switch Atheros AR8229)
  - 2.4 GHz, up to 27dBm        (Atheros AR9340)
  - 2x external, detachable antennas
  - 7x LED (5 programmable in ath79), 1x GPIO button (Reset)

Known Issues:

  - Sysupgrade from ar71xx no longer possible
  - Ethernet LEDs stay on solid when connected, not programmable

MAC addresses:

  eth0/eth1  *:7b   art 0x0/0x6
  wlan       *:7a   art 0x1002

  The device label lists both addresses, WLAN MAC and ETH MAC,
  in that order.

  Since 0x0 and 0x6 have the same content, it cannot be
  determined which is eth0 and eth1, so we chose 0x0 for both.

Installation:

  2 ways to flash factory.bin from OEM:

  - Connect ethernet directly to board (the non POE port)
      this is LAN for all images
  - if you get Failsafe Mode from failed flash:
      only use it to flash Original firmware from Engenius
      or risk kernel loop which requires serial cable

  Method 1: Firmware upgrade page:

    OEM webpage at 192.168.1.1
    username and password "admin"
    In upper right select Reset
    "Restore to factory default settings"
    Wait for reboot and login again
    Navigate to "Firmware Upgrade" page from left pane
    Click Browse and select the factory.bin image
    Upload and verify checksum
    Click Continue to confirm and wait 3 minutes

  Method 2: Serial to load Failsafe webpage:

    After connecting to serial console and rebooting...
    Interrupt boot with any key pressed rapidly
    execute `run failsafe_boot` OR `bootm 0x9fdf0000`
    wait a minute
    connect to ethernet and navigate to
    "192.168.1.1/index.htm"
    Select the factory.bin image and upload
    wait about 3 minutes

  *If you are unable to get network/LuCI after flashing*
  You must perform another factory reset:

    After waiting 3 minutes or when Power LED stop blinking:

    Hold Reset button for 15 seconds while powered on
    or until Power LED blinks very fast

    release and wait 2 minutes

Return to OEM:

  If you have a serial cable, see Serial Failsafe instructions

  *DISCLAIMER*
  The Failsafe image is unique to this model.
  The following directions are unique to this model.
  DO NOT downgrade to ar71xx this way, can cause kernel loop

  The easiest way to return to the OEM software is the Failsafe image
  If you dont have a serial cable, you can ssh into openwrt and run

  `mtd -r erase fakeroot`

  Wait 3 minutes
  connect to ethernet and navigate to 192.168.1.1/index.htm
  select OEM firmware image from Engenius and click upgrade

TFTP Recovery:

  For some reason, TFTP is not reliable on this board.
  Takes many attempts, many timeouts before it fully transfers.

  Starting with an initramfs.bin:

  Connect to ethernet
  set IP address and TFTP server to 192.168.1.101
  set up infinite ping to 192.168.1.1
  rename the initramfs.bin to "vmlinux-art-ramdisk" and host on TFTP server
  disconnect power to the board
  hold reset button while powering on board for 8 seconds

  Wait a minute, power LED should blink eventually if successful
  and a minute after that the pings should get replies
  You have now loaded a temporary Openwrt with default settings temporarily.
  You can use that image to sysupgrade another image to overwrite flash.

Format of OEM firmware image:

  The OEM software of ENS202EXT is a heavily modified version
  of Openwrt Kamikaze bleeding-edge. One of the many modifications
  is to the sysupgrade program. Image verification is performed
  simply by the successful ungzip and untar of the supplied file
  and name check and header verification of the resulting contents.
  To form a factory.bin that is accepted by OEM Openwrt build,
  the kernel and rootfs must have specific names...

    openwrt-senao-ens202ext-uImage-lzma.bin
    openwrt-senao-ens202ext-root.squashfs

  and begin with the respective headers (uImage, squashfs).
  Then the files must be tarballed and gzipped.
  The resulting binary is actually a tar.gz file in disguise.
  This can be verified by using binwalk on the OEM firmware images,
  ungzipping then untaring, and by swapping headers to see
  what the OEM upgrade utility accepts and rejects.

Note on the factory.bin:

  The newest kernel is too large to be in the kernel partition

  the new ath79 kernel is beyond   1592k
  Even ath79-tiny is               1580k

  Checksum fails at boot because the bootloader (modified uboot)
  expects kernel to be 1536k. If the kernel is larger, it gets
  overwritten when rootfs is flashed, causing a broken image.
  The mtdparts variable is part of the build and saving a new
  uboot environment will not persist after flashing.
  OEM version might interact with uboot or with the custom
  OEM partition at 0x9f050000.

  Failed checksums at boot cause failsafe image to launch,
  allowing any image to be flashed again.

  HOWEVER: one should not install older Openwrt from failsafe
  because it can cause rootfs to be unmountable,
  causing kernel loop after successful checksum.
  The only way to rescue after that is with a serial cable.

  For these reasons, a fake kernel (OKLI kernel loader)
  and fake squashfs rootfs is implemented to take care of
  the OEM firmware image verification and checksums at boot.
  The OEM only verifies the checksum of the first image
  of each partition respectively, which is the loader
  and the fake squashfs. This completely frees
  the "firmware" partition from all checks.

  virtual_flash is implemented to make use of the wasted space.
  this leaves only 2 erase blocks actually wasted.

  The loader and fakeroot partitions must remain intact, otherwise
  the next boot will fail, redirecting to the Failsafe image.

  Because the partition table required is so different
  than the OEM partition table and ar71xx partition table,
  sysupgrades are not possible until one switches to ath79 kernel.

Note on sysupgrade.tgz:

  To make things even more complicated, another change is needed to
  fix an issue where network does not work after flashing from either
  OEM software or Failsafe image, which implants the OEM (Openwrt Kamikaze)
  configuration into the jffs2 /overlay when writing rootfs from factory.bin.

  The upgrade script has this:

    mtd -j "/tmp/_sys/sysupgrade.tgz" write "${rootfs}" "rootfs"

  However, it also accepts scripts before and after:

    before_local="/etc/before-upgradelocal.sh"
    after_local="/etc/after-upgradelocal.sh"
    before="before-upgrade.sh"
    after="after-upgrade.sh"

  Thus, we can solve the issue by making the .tgz an empty file
  by making a before-upgrade.sh in the factory.bin

Note on built-in switch:

  There is two ports on the board, POE through the power supply brick,
  the other is on the board. For whatever reason, in the ar71xx target,
  both ports were on the built-in switch on eth1. In order to make use
  of a port for WAN or a different LAN, one has to set up VLANs.

  In ath79, eth0 and eth1 is defined in the DTS so that the
  built-in switch is seen as eth0, but only for 1 port
  the other port is on eth1 without a built-in switch.

  eth0: switch0
    CPU is port 0
    board port is port 1

  eth1: POE port on the power brick

  Since there is two physical ports,
  it can be configured as a full router,
  with LAN for both wired and wireless.

  According to the Datasheet, the port that is not on the switch
  is connected to gmac0. It is preferred that gmac0 is chosen as WAN
  over a port on an internal switch, so that link status can pass
  to the kernel immediately which is more important for WAN connections.

Signed-off-by: Michael Pratt <mpratt51@gmail.com>
[apply sorting in 01_leds, make factory recipe more generic, create common
device node, move label-mac to 02_network, add MAC addresses to commit
message, remove kmod-leds-gpio, use gzip directly]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>