Boot Configuration and eMMC Setup for Device Recovery
Configuring the boot settings on an eMMC chip is a critical first step in restoring or initializing a device. This involves modifying three key extCSD registers:
- Boot Partition [179]: Specifies which eMMC partition is used for boot operations.
- Bus Config [177]: Defines the width and boot mode settings.
- H/W Reset Function [162]: Controls the reset functionality of the eMMC.
For example:
- Boot configuration:
PARTITION_CONFIG: 0x00
(No boot partition configured). - Boot bus config [177]:
0x00
(1-bit width). - H/W reset function [RST_N_FUNCTION]:
0x01
.
These registers can be set using one of four methods:
- From a previously saved extCSD file from the same device.
- From an extCSD file saved during eMMC firmware updates.
- Using predefined options.
- Manual configuration.
Writing Boot Configurations
Using tools like Repair ExtCSD -> Only Boot Config, the following values can be written:
- Boot config:
0x48, 0x00, 0x01
for registers 179, 177, and 162, respectively.
Platform-Specific Configuration Instructions
1. MediaTek (MTK)
- Boot Config:
0x48, 0x00, 0x01
- Ensure ROM2/3/RPMB sizes are ≤2MB for MT6589/8389 processors.
- Options:
- Write Boot Config and erase eMMC (device detected as MTK USB Port).
- Write Boot Config and preloader to ROM2/3 (device detected as MTK Virtual VCOM Port).
- Use backups for ROM2/3 and restore via "eMMC General."
In most cases, MTK devices can be flashed using the MTK FlashTool.
2. Intel
- Boot Config:
0x00, 0x00, 0x0x
or0x00, 0x06, 0x01
. - Steps:
- Create a GP1 partition if required.
- Write Boot Config, erase eMMC, and use xFSTK utility to flash the bootloader.
Devices booting into DroidBoot can be further flashed via firmware.
3. Qualcomm
- Boot Config:
0x00, 0x00, 0x0x
or0x38, 0x00, 0x01
. - Options:
- Write Boot Config, erase eMMC (detected as HS QD9008 Loader).
- Use "Write by Vendor" to flash bootloaders and firmware sections.
Devices can then boot into FastBoot or Recovery for complete firmware restoration.
4. Exynos
- Boot Config:
0x48, 0x01, 0x0x
. - Options:
- Erase eMMC and use a prepared SD card for recovery.
- Flash parts of the firmware for FastBoot or Recovery access.
5. HiSilicon
- Boot Config:
0x08, 0x02, 0x01
. - Options:
- Write Boot Config and firmware sections for FastBoot/Recovery.
- Write ROM2 and parts of ROM1 dump (100-500MB).
6. SpreadTrum
- Boot Config:
0x08, 0x00, 0x0x
. - Options:
- Flash firmware via "Write by Vendor - SpreadTrum."
- Use ROM2/3 dumps and parts of ROM1 for recovery.
7. Broadcom
- Boot Config:
0x00, 0x00, 0x0x
. - Options:
- Write Boot Config and firmware for FastBoot/Recovery.
- Flash ROM2 and part of ROM1 dump (100-500MB).
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