1. Das U-Boot 3/25/2017 Slide NOTE:
Help the field to keep the messages clean and clear to customers, and add speaker notes for their use. Include at least major bullet points to be used as discussion points with customers during a presentation.

2. Boot Terminology Loader Bootloader / Bootstrap Boot PROM Boot Manager
3/25/2017
Boot Terminology
Loader
Program that moves bits from non volatile memory to memory and then transfers CPU control to the newly “loaded” bits (executable)
Bootloader / Bootstrap
Program that loads the “first program” (the kernel)
Boot PROM
Persistent code that is “already loaded” on power-up
Boot Manager
Program that lets you choose the “first program” to load
Loading is an important and often over-looked OS concept. Loading is increasingly accomplished “on-demand” via dynamic linking-loaders. The Linux kernel module mechanism is essentially an advanced application of dynamic linking/loading.
People often mistakenly think that “bootstrap” refers to boot laces.
The “bootstrap” metaphor refers to the nonsensical image of someone lifting themselves up off the ground by their own bootstrap. The impossibility of this image adds to the mystery of the boot process.
There are lots of related types of “firmware”: ROM, PROM, EPROM, EEPROM, NVRAM, Flash RAM and who knows what else. PROM in “Boot PROM” or “PROM Monitor” is used informally. In the SPARC architecture, these are actually contained in EEPROMs.
The phrase “first program” is in quotes for a reason. Often the first program loaded is itself a boot manager, like LILO.
LILO introduces the concept of “chain loaders”. Why not have one loader load another loader which might load another loader…

3. What’s a Loader? memory loader bits flash cpu bits
3/25/2017
What’s a Loader?
A program that moves bits from flash or disk to memory and then transfers control to the newly loaded bits (executable).
loader
memory
bits
flash
bits
cpu
A great reference is “Linkers & Loaders” by John Levine Morgan Kaufmann 2000.
Loaders are also sometimes responsible for allocating memory, setting protection bits, updating memory maps, etc.

4. Loading through Das U-boot
SDRAM
Memory
0x1000
Reset
CPU
Kernel
Root
File-System
ROM
BMODE 00
ByPass PROM 0x
Bootloader
uboot
Bootloader
uboot
Kernel Image
Optional
compressed
Root File System

5. 3/25/2017
Das U-Boot
The "Universal Bootloader" ("Das U-Boot") is a monitor/MicroOS program.
Started in October of 1999 by Dan Malek, supported by Wolfgang Denk (Denx Engineering) as of July 2000
Free Software: full source code under GPL
Hosted on SourceForge: ·
Production quality:
Used as default boot loader by several board vendors ·
Portable and easy to port and to debug
Many supported architectures: PPC, ARM, MIPS, x86, m68k, NIOS, Microblaze, and Blackfin
More than 216 boards supported by public source tree
Uboot – very powerful and supports:
Network boot
Flash based boot
Multiple protocols
Splash screen (display image in CRT)

6. Blackfin U-boot features

7. Where to get U-boot sources

8. User Interface (1)
U-Boot uses a simple command line interface (CLI), usually over a serial console port.
Two different command interpreters are available:
Simple CLI ·
Bourne compatible shell (HUSH shell from Busybox) ·
Configuration parameters and commands / command sequences (scripts !) can be stored in "environment variables" which can be saved to non-volatile storage (flash, EEPROM, NVRAM, etc.)

9. 3/25/2017
User Interface (2)
U-Boot supports many different ways to load and boot an image.
Serial Port: "loads" (S-Record), "loadb" (Kermit binary protocol)
Ethernet: "tftp", "bootp", "dhcp", "nfs“
Harddisk, CDROM: "ide read"
CompactFlash card etc.: "ide read"
USB Mass Storage Device: "usb read"
SCSI Disk and CDROM: "scsi read"
NAND flash with JFFS2 filesystem: "nboot"
Disk on Chip: "doc read"
PCI Bus: copy
Commands
Memory Commands
Flash Memory Commands
Execution Control Commands
User interface for Uboot – command line for serial port either net.
Flexible and powerful – can configure your system and only compile what you need.
Network Commands
Bootp
Cdp
dhcp
loadb
oads
Nfs
ping
rarpboot
tftpboot
Environment Variables Commands
Printenv
saveenv
Askenv
setenv
run
Bootd
Information Commands
bdinfo
coninfo
flinfo
iminfo
imls
help

10. Boot Image Image: Header: Actions: Header + Payload
Creation Timestamp
Data Load Address
Entry Point Address
Data CRC Checksum
Operating System
CPU architecture
Image Type
Compression Type
Image Name
Actions:
test CPU architecture and OS
test checksum (optional)
if compressed, uncompress
copy to load address
prepare boot arguments
start at entry point

11. Image Types Standalone Programs OS Kernel Images RAMDisk Images
3/25/2017
Image Types
Standalone Programs
OS Kernel Images
RAMDisk Images
Multi-File Images
Firmware Images
Script files
Standalone Programs
Directly runnable in the environment provided by U-Boot; it is expected that you can continue to work in U-Boot after return from the Standalone Program.
OS Kernel Images
Usually images of some Embedded OS which will take over control completely. Usually these programs will install their own set of exception handlers, device drivers, set up the MMU, etc.
RAMDisk Images
Data blocks, and their parameters (address, size) are passed to an OS kernel that is being started.
Multi-File Images
Contain several images, typically an OS (Linux) kernel image and one or more data images like RAMDisks. This construct is useful for instance when you want to boot over the network using BOOTP etc., where the boot server provides just a single image file, but you want to get for instance an OS kernel and a RAMDisk image.
Firmware Images
Binary images containing firmware (like U-Boot or FPGA images) which usually will be programmed to flash memory.
Script files
Command sequences that will be executed by U-Boot's command interpreter; this feature is especially useful when you configure U-Boot to use a real shell (hush) as command interpreter.

12. Configuring U-Boot
Configuration depends on the combination of board and CPU type; all such information is kept in a configuration file "include/configs/<board_name>.h".
Example: For a STAMP board, all configuration settings are in "include/configs/stamp.h".
For all supported boards there are ready-to-use default configurations available; just type "make <board_name>_config".
Example: For the STAMP board type:
cd u-boot
make stamp_config
For configuration details, check the U-Boot README and the Wiki – docs.blackfin.uclinux.org

13. Building U-Boot (1/2)
Building U-Boot has been tested in x86 cross environments (running RedHat 6.x and 7.x Linux, SuSE 9.0 and 9.1 Linux on x86).
It is assumed that you have the GNU cross compiling tools available in your path and named with a prefix of “bfin-elf". If this is not the case, you must change the definition of CROSS_COMPILE in Makefile.

14. Building U-Boot (2/2)
U-Boot is intended to be simple to build. After installing the sources you must configure U-Boot for one specific board type. This is done by typing:
cd u-boot
make clean; make mrproper
make stamp_config
make all
You should get some working U-Boot images ready for download to / installation on your system:
"u-boot.bin" is a raw binary image
"u-boot" is an image in ELF binary format
"u-boot.srec" is in Motorola S-Record format

15. U-Boot Source Code Official U-boot Source Code is at:
3/25/2017
U-Boot Source Code
Official U-boot Source Code is at:
Unofficial Blackfin Branch is at:
U-Boot uses a 3 level version number containing a version, a sub-version, and a patchlevel "U-Boot " means:
version "2",
sub-version "34", and
patchlevel "4".
The patchlevel is used to indicate certain stages of development between released versions, i. e. officially released versions of U-Boot will always have a patchlevel of "0".
Location of Uboot source code…

16. More U-Boot information
The U-Boot project is hosted at Sourceforge:
There is a pretty active u-boot-users mailing list.
The Mailing list archive can be viewed at sourceforge.net
The DENX U-Boot and Linux Guide is a Wiki based documentation documenting U-Boot and its interaction with Linux. It can be viewed (and improved) at The whole DULG web packed into a single HTML page or a PDF file is also available (PowerPC is the example)
The current README file can be viewed through viewcvs at sourceforge.net

17. Backup slides

18. Das U-Boot Introduction Porting Guide Directory Structure
Material in this presentation is taken from the project README file, and from and

19. Supported Platforms Architecture Processor Number of Boards PPC 5xx 2
5xxx 6
8xx 71
824x 15
826x 26
85xx 3
7xx/74xx 11
4xx 38
ARM
StrongARM 5
ARM720T
ARM92xT
Architecture
Processor
Number of Boards
ARM (cont)
S3C44B0 1
AT91RM9200
XScale 8
x86
SC520 2
m68k
Coldfire
MIPS32
4Kc
Au1x00 3
MIPS64
5Kc
NIOS32
Microblaze
Blackfin
BF533/BF535

20. Das U-boot Design Principles
Easy to port to new architectures, new processors, and new boards
Easy to debug: serial console output as soon as possible ·
Features and commands configurable ·
As small as possible ·
As reliable as possible

21. Image Support
Although U-Boot can support any OS or standalone application, the main focus has always been on Linux during the design of U-Boot.
U-Boot includes many features that so far have been part of some special "boot loader" code within the Linux kernel. Also, any "initrd" images to be used are no longer part of one big Linux image; instead, kernel and "initrd" are separate images.

22. U-Boot Basic Command Set (1/4)
Information Commands
bdinfo - print Board Info structure ¨
coninfo - print console devices and informations
flinfo - print FLASH memory information
iminfo - print header information for application image
imls - list all images found in flash
help - print online help
Memory Commands
base - print or set address offset
crc32 - checksum calculation
cmp - memory compare
cp - memory copy
md - memory display
mm - memory modify (auto-incrementing)
mtest - simple RAM test
mw - memory write (fill)
nm - memory modify (constant address)
loop - infinite loop on address range
Flash Memory Commands
cp - memory copy (program flash)
flinfo - print FLASH memory information
erase - erase FLASH memory
protect - enable or disable FLASH write protection
Execution Control Commands
autoscr - run script from memory
bootm - boot application image from memory
bootelf - Boot from an ELF image in memory
bootvx - Boot vxWorks from an ELF image
go - start application at address 'addr'

23. U-Boot Basic Command Set (2/4)
Network Commands
bootp - boot image via network using BOOTP/TFTP protocol
cdp - Perform Cisco Discovery Protocol network configuration
dhcp - invoke DHCP client to obtain IP/boot params
loadb - load binary file over serial line (kermit mode)
loads - load S-Record file over serial line
nfs - boot image via network using NFS protocol
ping - send ICMP ECHO_REQUEST to network host
rarpboot- boot image via network using RARP/TFTP protocol
tftpboot- boot image via network using TFTP protocol
Environment Variables Commands
printenv- print environment variables
saveenv - save environment variables to persistent storage
askenv - get environment variables from stdin
setenv - set environment variables
run - run commands in an environment variable
bootd - boot default, i.e., run 'bootcmd'

24. U-Boot Basic Command Set (3/4)
Filesystem Support (FAT, cramfs, JFFS2, Reiser)
chpart - change active partition
fsinfo - print information about filesystems
fsload - load binary file from a filesystem image
ls - list files in a directory (default /)
fatinfo - print information about filesystem
fatls - list files in a directory (default /)
fatload - load binary file from a dos filesystem
nand - NAND flash sub-system
reiserls- list files in a directory (default /)
reiserload- load binary file from a Reiser filesystem
Special Commands
i2c - I2C sub-system
doc - Disk-On-Chip sub-system
dtt - Digital Thermometer and Themostat
eeprom - EEPROM sub-system
fpga - FPGA sub-system
ide - IDE sub-system
kgdb - enter gdb remote debug mode
diskboot- boot from IDE device
icache - enable or disable instruction cache
dcache - enable or disable data cache
diag - perform board diagnostics (POST code)
log - manipulate logbuffer
pci - list and access PCI Configuraton Space
regdump - register dump commands
usb - USB sub-system
sspi - SPI utility commands

25. U-Boot Basic Command Set (4/4)
Miscellaneous Commands
bmp - manipulate BMP image data ¨
date - get/set/reset date & time ¨
echo - echo args to console ¨
exit - exit script ¨
kbd - read keyboard status ¨
in - read data from an IO port ¨
out - write datum to IO port ¨
reset - Perform RESET of the CPU ¨
sleep - delay execution for some time ¨
test - minimal test like /bin/sh ¨
version - print monitor version ¨
wd - check and set watchdog ¨
? - alias for 'help' ¨