systems engineering understanding uclinux device drivers
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The World Leader in High Performance Signal Processing Solutions
Das U-Boot
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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
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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).
cpu
flash
bits
memory
bits
loader
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Loading through Das U-boot
SDRAMMemory
RootFile-System
Kernel
ROM
Kernel Image
Bootloaderuboot
Root File System
Reset
Bootloaderuboot
CPU
BMODE 00
ByPass PROM
0x20000000
0x1000
Optional
compressed
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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: http://sourceforge.net/projects/u-boot ·
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
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Blackfin U-boot features
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Where to get U-boot sources
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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.)
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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 Environment Variables
Commands Printenv saveenv Askenv setenv run Bootd
Memory Commands Flash Memory Commands Execution Control
Commands
Network Commands Bootp Cdp dhcp loadb oads Nfs ping rarpboot tftpboot
Information Commands bdinfo coninfo flinfo iminfo imls help
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Boot Image
Image: Header + Payload
Header: 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
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Image TypesStandalone Programs
OS Kernel Images
RAMDisk Images
Multi-File Images
Firmware Images
Script files
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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
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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.
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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 mrpropermake stamp_configmake 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
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U-Boot Source Code
Official U-boot Source Code is at: http://sourceforge.net/projects/u-boot
Unofficial Blackfin Branch is at: http://blackfin.uclinux.org/projects/uboot533
U-Boot uses a 3 level version number containing a version, a sub-version, and a patchlevel "U-Boot-2.34.5" 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".
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More U-Boot information
The U-Boot project is hosted at Sourceforge: http://sourceforge.net/projects/u-boot
There is a pretty active u-boot-users mailing list.
The Mailing list archive can be viewed at sourceforge.net http://lists.sourceforge.net/lists/listinfo/u-boot-users/
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 www.denx.de. 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
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Backup slides
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Das U-Boot
IntroductionPorting GuideDirectory Structure
Material in this presentation is taken from the project README file, and from http://www.denx.de/twiki/bin/view/UBootdoc/Presentation and http://www.denx.de/twiki/bin/view/DULG/Manual
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Supported Platforms
11ARM92xT
3ARM720T
5StrongARMARM
384xx
117xx/74xx
385xx
26826x
15824x
718xx
65xxx
25xxPPC
Number of BoardsProcessorArchitecture
3BF533/BF535Blackfin
1 Microblaze
3 NIOS32
15KcMIPS64
3Au1x00
24KcMIPS32
2Coldfirem68k
2SC520x86
8XScale
1AT91RM9200
1S3C44B0ARM (cont)
Number of BoardsProcessorArchitecture
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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
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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.
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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'
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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'
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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
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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' ¨
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