U-Boot for the ASUS Transformer device family
DISCLAMER!
Moving your ASUS Transformer to use U-Boot assumes replacement
of the vendor ASUS bootloader. Vendor Android firmwares will no longer be
able to run on the device. This replacement IS reversible.
Quick Start
Build U-Boot
Process U-Boot
Flashing U-Boot into the eMMC
Flashing U-Boot into the SPI flash
Boot
Self Upgrading
Build U-Boot
U-Boot features ability to detect transformer device model on which it is loaded. The list of supported devices include: - ASUS Transformer Prime TF201 - ASUS Transformer Pad (3G/LTE) TF300T/TG/TL - ASUS Transformer Infinity TF700T - ASUS Portable AiO P1801-T - ASUS VivoTab RT TF600T
$ export CROSS_COMPILE=arm-linux-gnueabi-
$ make transformer_t30_defconfig
$ 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
tablet’s individual SBK to continue.
Permanent installation can be performed either by using the nv3p protocol or by pre-loading just built U-Boot into RAM.
Processing for the NV3P protocol
$ 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 tf201 --sbk <your sbk>
where SBK has next form 0xXXXXXXXX
0xXXXXXXXX
0xXXXXXXXX
0xXXXXXXXX
The script will produce a repart-block.bin
ready to flash.
Processing for pre-loaded U-Boot
The procedure is the same, but the --split
argument is used with the
re-crypt.py
. The script will produce bct.img
and ebt.img
ready
to flash.
Flashing U-Boot into the eMMC
DISCLAMER!
All questions related to NvFlash should be asked in the proper
place. NOT HERE! Flashing U-Boot will erase all eMMC, so make a backup before!
Permanent installation can be performed either by using the nv3p protocol or by pre-loading just built U-Boot into RAM.
Flashing with the NV3P protocol
Nv3p is a custom Nvidia protocol used to recover bricked devices. Devices can
enter it either by using wheelie
with the correct blob.bin
file or by
pre-loading vendor bootloader with the Fusée Gelée.
With nv3p, repart-block.bin
is used. It contains BCT and a bootloader in
encrypted state in form, which can just be written RAW at the start of eMMC.
$ wheelie --blob blob.bin
$ nvflash --resume --rawdevicewrite 0 1024 repart-block.bin
When flashing is done, reboot the device.
Flashing with a pre-loaded U-Boot
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.
Flashing U-Boot into the SPI Flash
Some of Transformers use a separate 4 MB SPI flash, which contains all data required for boot. It is flashed from within U-Boot itself, preloaded into RAM using Fusée Gelée.
After creating your repart-block.bin
you have to place it on a 1st partition
of microSD card formated in fat. Then insert this microSD card into your tablet
and boot it using Fusée Gelée and U-Boot, which was included into
repart-block.bin
, while booting you must hold the volume down
button.
The process should take less than a minute, if everything goes correctly,
on microSD will appear spi-flash-backup.bin
file, which is the dump of your
SPI Flash content and can be used to restore UEFI, do not lose it, tablet will
power itself off.
Self-updating of U-Boot is performed by placing u-boot-dtb-tegra.bin
on 1st
partition of microSD, inserting it into the tablet and booting with a pressed
volume down
button.
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 tablet. 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.