mediatek: filogic: add support for Xiaomi AX3000T

mediatek: filogic: add support for Xiaomi AX3000T

  **SoC**: MediaTek MT7981B 2x A53
  **Flash**: ESMT F50L1G41LB 128MB
  **RAM**: NT52B128M16JR-FL 256MB
  **Ethernet**: 4x 10/100/1000 Mbps
  **Switch**: MediaTek MT7531AE
  **WiFi**: MediaTek MT7976C
  **Buttons**: Reset, Mesh
  **Power**: DC 12V 1A

1. Get ssh access. Supported stock firmware **1.0.47**
   ```
   curl -X POST "http://192.168.31.1/cgi-bin/luci/;stok=*******/api/misystem/arn_switch" -d "open=1&model=1&level=%0Anvram%20set%20ssh_en%3D1%0A"
   curl -X POST "http://192.168.31.1/cgi-bin/luci/;stok=*******/api/misystem/arn_switch" -d "open=1&model=1&level=%0Anvram%20commit%0A"
   curl -X POST "http://192.168.31.1/cgi-bin/luci/;stok=*******/api/misystem/arn_switch" -d "open=1&model=1&level=%0Ased%20-i%20's%2Fchannel%3D.*%2Fchannel%3D%22debug%22%2Fg'%20%2Fetc%2Finit.d%2Fdropbear%0A"
   curl -X POST "http://192.168.31.1/cgi-bin/luci/;stok=*******/api/misystem/arn_switch" -d "open=1&model=1&level=%0A%2Fetc%2Finit.d%2Fdropbear%20start%0A"
   curl -X POST "http://192.168.31.1/cgi-bin/luci/;stok=********/api/misystem/arn_switch" -d "open=1&model=1&level=%0Apasswd%20-d%20root%0A
   ```

2. Backup stock partitions
   ```
   nanddump -f /tmp/BL2.bin /dev/mtd1
   nanddump -f /tmp/Nvram.bin /dev/mtd2
   nanddump -f /tmp/Bdata.bin /dev/mtd3
   nanddump -f /tmp/Factory.bin /dev/mtd4
   nanddump -f /tmp/FIP.bin /dev/mtd5
   nanddump -f /tmp/ubi.bin /dev/mtd8
   nanddump -f /tmp/KF.bin /dev/mtd12
   ```
   Then transfer them to your computer in a safe place.

3. Get firmware information `cat /proc/cmdline`

4. Copy openwrt-mediatek-filogic-xiaomi_mi-router-ax3000t-initramfs-factory.ubi to **/tmp** and flash
   If **firmware=0**
   ```
   ubiformat /dev/mtd9 -y -f /tmp/openwrt-mediatek-filogic-xiaomi_mi-router-ax3000t-initramfs-factory.ubi
   nvram set boot_wait=on
   nvram set uart_en=1
   nvram set flag_boot_rootfs=1
   nvram set flag_last_success=1
   nvram set flag_boot_success=1
   nvram set flag_try_sys1_failed=0
   nvram set flag_try_sys2_failed=0
   nvram commit
   reboot
   ```
   If **firmware=1**
   ```
   ubiformat /dev/mtd8 -y -f /tmp/openwrt-mediatek-filogic-xiaomi_mi-router-ax3000t-initramfs-factory.ubi
   nvram set boot_wait=on
   nvram set uart_en=1
   nvram set flag_boot_rootfs=0
   nvram set flag_last_success=0
   nvram set flag_boot_success=1
   nvram set flag_try_sys1_failed=0
   nvram set flag_try_sys2_failed=0
   nvram commit
   reboot
   ```

   Then reboot your router, it should boot to the OpenWrt initramfs system now.

5. Flash openwrt-mediatek-filogic-xiaomi_mi-router-ax3000t-squashfs-sysupgrade.bin
   `sysupgrade -n /tmp/openwrt-mediatek-filogic-xiaomi_mi-router-ax3000t-squashfs-sysupgrade.bin`

1. Flash openwrt-mediatek-filogic-xiaomi_mi-router-ax3000t-ubootmod-initramfs-recovery.itb
   `ubiformat /dev/mtd8 -y -f /tmp/openwrt-mediatek-filogic-xiaomi_mi-router-ax3000t-ubootmod-initramfs-recovery.itb`

   `reboot`

2. Install kmod-mtd-rw
   `opkg update && opkg install kmod-mtd-rw`

   `insmod /lib/modules/$(uname -r)/mtd-rw.ko i_want_a_brick=1`

3. Format ubi and create new ubootenv volume
   ```
   ubidetach -p /dev/mtd8; ubiformat /dev/mtd8 -y; ubiattach -p /dev/mtd8
   ubimkvol /dev/ubi0 -n 0 -N ubootenv -s 128KiB
   ubimkvol /dev/ubi0 -n 1 -N ubootenv2 -s 128KiB
   ```

4. *(Optional **-10Mb** free space) Add recovery boot feature.*
   ```
   ubimkvol /dev/ubi0 -n 2 -N recovery -s 10MiB
   ubiupdatevol /dev/ubi0_2 /tmp/openwrt-mediatek-filogic-xiaomi_mi-router-ax3000t-ubootmod-initramfs-recovery.itb
   ```

5. Flash Openwrt U-Boot
   ```
   mtd write /tmp/openwrt-mediatek-filogic-xiaomi_mi-router-ax3000t-ubootmod-preloader.bin BL2
   mtd write /tmp/openwrt-mediatek-filogic-xiaomi_mi-router-ax3000t-ubootmod-bl31-uboot.fip FIP
   ```

6. Flash openwrt-mediatek-filogic-xiaomi_mi-router-ax3000t-ubootmod-squashfs-sysupgrade.itb
   `sysupgrade -n /tmp/openwrt-mediatek-filogic-xiaomi_mi-router-ax3000t-ubootmod-squashfs-sysupgrade.itb`

1. Force flash openwrt-mediatek-filogic-xiaomi_mi-router-ax3000t-ubootmod-initramfs-recovery.itb
   `sysupgrade -F -n /tmp/openwrt-mediatek-filogic-xiaomi_mi-router-ax3000t-ubootmod-initramfs-recovery.itb`

2. Format ubi and Nvram
   ```
   ubidetach -p /dev/mtd8; ubiformat /dev/mtd8 -y; ubiattach -p /dev/mtd8
   mtd erase Nvram
   ```

3. Install kmod-mtd-rw
   `opkg update && opkg install kmod-mtd-rw`

   `insmod /lib/modules/$(uname -r)/mtd-rw.ko i_want_a_brick=1`

4. Flash stock images from backup
   ```
   mtd write /tmp/BL2.bin BL2
   mtd write /tmp/FIP.bin FIP
   mtd write /tmp/ubi.bin ubi
   ```
   Then reboot your router, waiting it finished rollback in minutes.

   `ubiformat /dev/mtd7 -y -f /tmp/ubi.bin`
   Then reboot your router, waiting it finished rollback in minutes.

Signed-off-by: Dim Fish <dimfish@gmail.com>
(cherry picked from commit 7dbcc1215a56cc1da68c81bf92d7efa174c5e051)