Relationship between Android X-loader and U-boot

This is the official document, you can refer to, I write these things just to give yourself a note, also for the use of a friend reference; official documents: http://omappedia.org/wiki/Bootloader_Project

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2012/09/14/5
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1: When a system is first booted, the CPU invokes the Reset vector to start
Code at a known location in ROM;
When the system starts for the first time, the Reset vector called by the CPU starts code in the ROM at a known position;

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2:
A) ROM code
Performs minimal clocks, memories and peripheral configuration; searches the booting
Devices for a valid booting image; loads the X-loader into SRAM and executes it;
Execute the minimum clock, memory and peripheral configurations, search for valid boot images of the boot device, and load X-loader
And execute it;

B) x-loader
Sets up the pin muxing; initializes clocks and memory; loads the U-boot
SDRAM and executes it;
Set pin multiplexing; initialize clock and memory; load U-boot to SDRAM and execute the program;
Fastboot flash xloader device/Ti/panda/xloader. Bin
=> Fl;

C) U-boot
Performs some addtional platform initialization; sets the boot arguments;
Passes control to the kernel image;
Execute some additional platform initialization; Set pilot parameters; pass control to the kernel image;

Fastboot flash bootloader device/Ti/panda/bootloader. bin => here bootloader. Bin is uboot (for ARM platform). Personal Understanding;

D) Kernel
Decompresses the kernel into SDRAM; sets up peripherals, such as LCD, HDMI, I2C bus,
USB, SD card, audio, etc; mounts the Linux filesystem that contains all;
Decompress the kernel to SDRAM and set peripheral devices, such as LCD, HDMI, I2C bus, USB, SD card, and audio. Install
Linux File System, which contains all;
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3: X-loader Overview

The X-loader is a small first stage bootloader derived from the U-boot base code.
It is loaded into the internal static RAM by the omap rom code. Due to the small
Size of the internal static RAM, the X-loader is stripped down to the essentials.
The X-loader configures the pin muxing, clocks, DDR, and serial console, so that
It can access and load the second stage bootloader (u-boot) into the DDR. This
Figure shows the code flow in the X-loader, beginning in start. S.

X-loader Overview

X-loader is a small first-stage Boot Loader from the basic U-boot code. It is loaded to the OMAP Rom
Static RAM in the code. Due to the small size of the internal static RAM, X-loader is the essentials to be detached. X-loader
Configuration pin multiplexing, clock, DDR, and serial console, so that it can access and load the second-stage Bootstrap program
(U-BOOT) for disarmament, demobilization and reintegration. This figure shows X-loader in the code stream and starts start. S.

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U-boot Overview

The U-boot is a second stage bootloader that is loaded by the X-loader into DDR.
It comes from das u-boot. The U-boot can perform CPU dependent and board dependent
Initialization and configuration not done in the X-loader. The U-boot also nodes
Fastboot functionality for partitioning and flashing the emmc. The U-boot runs on
The master CPU (cpu id 0), which is responsible for the initialization and
Booting; at the same time, the slave CPU (CPU Id 1) is held in the "wait
Event "state. This figure shows the code flow in the U-boot, beginning in
Start. S.

U-boot Overview

U-boot is the second-stage boot program, which is loaded from the das u-boot to the X-loader of the DDR. U-boot supports X-loader.
Initialization and configuration related to CPU and board cannot be completed; U-boot also includes fastboot functional partitions and flash memory
Emmc. The U-boot runs on the master CPU (cpu id 0), which is responsible for initialization and boot, at the same time, from the CPU (CPU ID
1) Status of the "Waiting event. The code stream shown in this figure starts in start. s of U-boot.

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