Amazon Fire 7 2019 (amazon-mustang)

Contributors

 * NoriTech

Maintainer

 * NoriTech

How to unlock bootloader
The bootloader can now be through a hardware method: https://forum.xda-developers.com/amazon-fire/orig-development/fire-7-2019-mustang-unbrick-downgrade-t3944365

How to enter flash mode
Press and hold +

Installation
Due to the fact that fastboot doesn't work even after using the amonet exploit, you will need to export the boot image and flash it with twrp. Then flash this dummy zip which will force twrp to reapply the amonet exploit.

Another option is exporting a flashable zip that can be flashed using twrp. Refer to Installation Guide for postmarketOS

Amonet
Amonet is an lk exploit used to boot an unsigned kernel. Sources of amonet are available here: https://github.com/xyzz/amonet/tree/mustang. This exploit is installed by a bootrom exploit. But probably some 2nd stage bootloader is a good idea.

Mainlining
There is some work on mt8163 mainline, for amazon-karnak, but it will be easy to get it on mustang. For now serial console and simplefb is working. Pwrap and pmic seems to be working. https://github.com/mt8163-mainline/linux

Device problems

 * Mainline is not yet usable.
 * Panfrost (driver for mali-t720) is wip, and not avalible in downstream (Merged in linux 5.2)
 * This device use exploit due to locked bootloader. See #Amonet.
 * This device's bl is not very good for running linux, due to it appends much of bad cmdline params, and some things in device tree.

Useful information

 * Serial/UART
 * 921600 baud 8N1
 * RX & TX pads are on the back of the board clearly marked. A cheap RS232-to-USB will work.

Please approach with caution since the display flex cable (top center) is glued onto the board but the board can be flipped over while it is connnected.