U-Boot for the Motorola Atrix 4G (MB860) and Droid X2 (MB870)

DISCLAMER! Moving your device to use U-Boot assumes replacement of the vendor bootloader. Vendor Android firmwares will no longer be able to run on the device. This replacement IS reversible if you have backups.

Quick Start

  • Prerequisites

  • Build U-Boot

  • Process U-Boot

  • Flashing U-Boot into the eMMC

  • Boot

  • Self Upgrading

Prerequisites

In order to work with RCM/APX mode, both devices require a factory cable which is made by routing 5V to the ID pin of a micro-USB cable (5v is applied to both ID and dedicated 5v). This way, the host PC can detect the device in RCM mode, and the device can operate without a battery.

Build U-Boot

Device support is implemented by applying config fragment to a generic board defconfig. Valid fragments are daytona.config and olympus.config.

$ export CROSS_COMPILE=arm-none-eabi-
$ make mot_defconfig olympus.config # For Atrix 4G
$ make

After the build succeeds, you will obtain the final u-boot-dtb-tegra.bin image, ready for further processing.

Process U-Boot

DISCLAMER! All questions related to the re-crypt work should be asked in re-crypt repo issues. NOT HERE!

re-crypt is a tool that processes the u-boot-dtb-tegra.bin binary into form usable by device. This process is required only on the first installation or to recover the device in case of a failed update. You need to know your device individual SBK to continue.

$ git clone https://gitlab.com/grate-driver/re-crypt.git
$ cd re-crypt # place your u-boot-dtb-tegra.bin here
$ ./re-crypt.py --dev olympus --sbk <your sbk> --split

where SBK has next form 0xXXXXXXXX 0xXXXXXXXX 0xXXXXXXXX 0xXXXXXXXX

The script will produce bct.img and ebt.img ready to flash.

Flashing U-Boot into the eMMC

DISCLAMER! All questions related to fusee-tools should be asked in the proper place. NOT HERE! Flashing U-Boot will erase all eMMC, so make a backup before!

U-Boot pre-loaded into RAM acts the same as when it was booted “cold”. Currently U-Boot supports bootmenu entry fastboot, which allows to write a processed copy of U-Boot permanently into eMMC.

While pre-loading U-Boot, hold the volume down button which will trigger the bootmenu. There, select fastboot using the volume and power buttons. After, on host PC, do:

$ fastboot flash 0.1 bct.img
$ fastboot flash 0.2 ebt.img
$ fastboot reboot

Device will reboot.

Boot

To boot Linux, U-Boot will look for an extlinux.conf on MicroSD and then on eMMC. Additionally, if the Volume Down button is pressed while booting, the device will enter bootmenu. Bootmenu contains entries to mount MicroSD and eMMC as mass storage, fastboot, reboot, reboot RCM, poweroff, enter U-Boot console and update bootloader (check the next chapter).

Flashing repart-block.bin eliminates vendor restrictions on eMMC and allows the user to use/partition it in any way the user desires.

Self Upgrading

Place your u-boot-dtb-tegra.bin on the first partition of the MicroSD card and insert it into the device. Enter bootmenu, choose update the bootloader option with the Power button and U-Boot should update itself. Once the process is completed, U-Boot will ask to press any button to reboot.