On Thu, 2008-08-07 at 21:26 +0200, Robert Schwebel wrote: > Hi Remy, > > On Tue, Aug 05, 2008 at 11:07:43PM +0200, Remy Bohmer wrote: > > This bootstrap package is required on at91sam* boards where > > dataflash/nandflash is used to boot from. In these cases the internal > > bootROM of the AT91 core is used to boot the board with. > > Can you elaborate, how exactly does this work?
the SAM9 has a 4Kbyte SRAM onchip. The ROM loader (also onchip) loads 4kbyte from DATAFLASH, NAND, USB or serial port, and than jumps to the loaded code. The bootstrap loader than initializes SDRAM, the CPU etc. and loads the real bootloader (or linux) and jumps to that. > > + The AT91Bootstrap application is a first level bootloader > > + for Atmel AT91SAM9 ARM Thumb-based microcontrollers. > > + It is a modular application and thus can be used to customize > > + the framework for a particular deployment strategy. AT91Bootstrap > > + also provides clear examples, for a particular device, on > > + how to perform basic static configurations, such as PMC and > > + PIOs. AT91Bootstrap can be easily configured using a higher > > + level protocol. > > + AT91Bootstrap integrates several sets of algorithms: > > + - Device initialization such as clock speed configuration, PIO > > settings, etc. > > + - Peripheral drivers such as PIO, PMC, SDRAMC, etc. > > + - Physical media algorithms such as DataFlash, NANDFlash, > > Parallel Flash, etc. > > + - File System drivers such as JFFS2, FAT, etc. > > + - Compression and Cipher algorithms > > + - Application Launcher for ELF, Linux, etc. > > + For example, using this set of algorithms, it is possible to > > + obtain a basic bootloader that is located in DataFlash and is > > + copied to internal SRAM by SAM-BA Boot. The bootloader performs > > + the processor initialization (PLLs, PIOs, SDRAMC, SPI), loads > > UBoot > > + from DataFlash sectors to SDRAM and then jumps to it. Somehow this help reads like a mix of at91bootstrap and u-boot info. AFAIK does the at91bootstrap (which is 4kbyte max.) not support filesystems, cipher algorithms, ELF, Linux, etc. - Erwin -- ptxdist mailing list ptxdist@pengutronix.de
