[U-Boot-Users] AT91 u-boot lowlevel init Dataflash

Marco Cavallini arm.linux at koansoftware.com
Tue Jun 6 10:38:40 CEST 2006

Andreas Schweigstill ha scritto:
> Dear Marco!
> Marco Cavallini schrieb:
>> Hi,
>> I am trying to use u-boot-1.1.4 with AT91RM9200 based board.
>> Using Parallel flash all works perfectly, but if I try using u-boot 
>> stored in Dataflash i face to some problems and comparing two cases I 
>> see that CPU clock are different.
>> Seems that is required a RomBoot provided by Atmel which launch u-boot.
>> Is it really necessary ?
>> Maybe I've miss an option that avoid RomBoot usage ?
> You can omit the RomBoot step if you are able to build an U-Boot which
> fits into ~12KB of the internal SRAM.
> RomBoot has to be adopted to your target hardware, especially for CPU
> clock and memory initialisation. The Atmel provided RomBoot can only be
> compiled with ARM ADS but there is also a GCC version available:
> http://www.teest.com/at91/romboot.tar.gz

thank you for answering.
I can't and I don't want to store anything into internal SRAM.
I simply want to use Dataflash AT45xxx instead of Parallel AT49xxx

I digged and found that RomBoot leaves the CPU speed at its initial safe 
state (slow).
Clocks: CPU 59 MHz, master 59 MHz, main 18.432 MHz

Then I added board_late_init into at91rm9200dk.c and there I've set 
PLLAR, PLLBR, MCKR like into lowlevel_init.S
Now my board boots with the desired clock speed.
Clocks: CPU 179 MHz, master 59 MHz, main 18.432 MHz

BTW I wonder if could be useful (and appreciated) if I should merge 
RomBoot settings into u-boot allowing u-boot to be the one and only 
loader for Dataflash too.

Marco Cavallini
Koan s.a.s. - Bergamo - ITALIA
Embedded and Real-Time Software Engineering
www.KoanSoftware.com   |    www.KaeilOS.com

More information about the U-Boot mailing list