BeagleBoard-xM Bootloaders

1. © 2014-17 SysPlay Workshops <workshop@sysplay.in>
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BeagleBoard-xM Bootloaders

2. 2© 2014-17 SysPlay Workshops <workshop@sysplay.in>
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What to Expect?
Beagle Booting Process
W's of X-Loader
BSP in X-Loader
W's of U-Boot
BSP in U-Boot

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General Booting of BeagleBoard
ROM
Code
Internal
ROM
X-Loader
Internal
SRAM
Internal
ROM
U-Boot
External
DDR
Kernel
External
DDR

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X-Loader

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W's of X-Loader
First stage bootloader for Beagle Board
Derived from u-boot – the second stage
bootloader
Named as MLO (Memory Loader) in filesystem.
Runs in an internal SRAM
Loads the second stage bootloader i.e. U-Boot

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Let's Get Down to Source Code

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BSP for X-Loader
cpu/omap3
board/omap3530beagle/omap3530beagle.c
board/omap3530beagle/platform.S
lib/board.c
include/configs/omap3530beagle.h

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U-Boot

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W's of U-Boot
Universal Bootloader (U-Boot)
An Open Source Bootloader
With minimal changes, can be ported for any board
GRUB/LILO
Designed with x-86 in mind
Huge in Size
Needs to be changed drastically for porting on other
architecture

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U-Boot Source Tree
arch – Architecture dependent Code
board – Board dependent Code
common – Environment & Command Line Code
doc – Documentation
drivers – Device specific Drivers
fs – File System support Code
include – Headers
lib – Compression, Encryption related Code
net – Minimal Network Stack
tools – U-Boot Utilities (mkimage is here)

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U-Boot Initialization Details
Bootloader starts its execution from flash /RAM
Hardware Diagnostics, like POST, …
Configuring the CPU speed, MMU setting, etc
Memory setup & initialization
Setting up interfacing ports like serial, VGA, …
Sets up the address of the boot parameters

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U-Boot Configuration
Creating a configuration file for the board
Adding an entry in the board.cfg
Architecture
CPU
Board
Vendor (May be NULL)
SoC (May be NULL)

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Let's Get Down to Source Code

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Which folders to look for?
include/asm/mach-types.h - machine id
arch/arm/include/asm/arch-omap3
cpu/armv7/omap3/board.c
ti/beagle/beagle.c
arch/arm/lib/board.c – specific to arm

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U-Boot Porting
Implies adding a new Board to U-Boot
That entails
Adding board specific code at the right places
Adding the new board directory under board/ with
Makefile
Initialization Code for the Board
Configuration Makefile
Adding the new board header under include/configs/ with
Configuration for the Board

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What all have learnt?
Beagle Booting Process
W's of X-Loader
BSP in X-Loader
W's of U-Boot
BSP in U-Boot

17. 17© 2014-17 SysPlay Workshops <workshop@sysplay.in>
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