U Boot or Universal Bootloader

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

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 loader flash bits memory bits

Loading through Das U-boot SDRAM Memory Root File-System Kernel ROM Kernel Image Bootloader uboot Root File System Reset Bootloader uboot CPU BMODE 00 ByPass PROM 0x20000000 0x1000 Optional compressed

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

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.)

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

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

Image Types Standalone Programs OS Kernel Images RAMDisk Images Multi-File Images Firmware Images Script files

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

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.

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

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".

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

Das U-Boot Introduction Porting Guide Directory 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

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

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

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.

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'

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'

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

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' ¨

U Boot or Universal Bootloader

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