Hi Steven,
It's totally okay with me.
Should we put all the init code into cpu/at91rm9200/{start.S} and use CONFIG_ and CFG_?
I'd put it all in start.S and not define any CONFIG for it. But one thing you might check is if it will start up when the clocks are already configured. In other words, make sure your new u-boot can be started from an already running u-boot. This is necessary because the AT91RM9200 can be started from SPI DataFlash (or EEPROM) which requires a preloader. The preloader sets up clocks for SDRAM, etc and then launches u-boot.
I have a sperate entry in a Makefile for compiling u-boot up to run in ram so that I can fire a new u-boot while inside u-boot:
ram: cd u-boot-0.4.0; \ echo TEXT_BASE = 0x21fa0000 > board/at91rm9200dk/config.mk; \ make at91rm9200dk_config; \ make; \ cp -f u-boot.bin /tftpboot
And then from u-boot I do:
tftp 21fa0000 u-boot.bin # load u-boot go 21fa0000 # run u-boot
Or should every AT91 based board copy the same code again and again into thier own subdirectory?
I'd make it (optimistically) so they didn't have to copy.
Thanks for your work!
Rick
Hi Rick et al.,
as I mentioned before U-Boot is running on our AT91RM9200 based board. I went down the path ATMEL was suggesting. They use this memory map on their eval board AT91RM9200DK:
24k Boot Image 32KB free 8KB Environment 64KB gzipped U-Boot image
The "Boot image" is a small (11k) piece of code which initialises clocks, flash, SDRAM and serial port. Then it decompresses the "gzipped U-Boot image" into SDRAM and jumps to it. The reason for that seems to be:
We chose, to put a compressed boot due to memory mapping constraints. We need to keep a sector for environment variables the 8Kbyte-size sector is enough.
They probably overlooked that you could embedded the environment into U-Boot. By using a correct u-boot.lds linker file one can reserve an 8Kbyte-size sector in the middle of U-Boot. So instead one could use this memory map:
56KB U-Boot 8KB Environment 64KB U-Boot
using the same 128KB of flash.
Since the CPU was setup by the bootloader there's no init and relocation code for the AT91RM9200 in U-Boot (yet).
So I spend a day, "wrote" some init and relocation code and now U-Boot is starting directly from flash and relocates itself to RAM. No Preboot needed. Nor gzipped image of U-Boot.
I would like to change the official U-Boot code for the AT91RM9200 and AT91RM9200DK so that it can be used without the need of another bootloader. This way it would be a lot easier for people to port U-Boot to their hardware.
What do you think? Anyone interessted?
I'd love to hear suggestion, where to put specific parts of the init code. Other ARM cpus use a board specific memsetup.S file. For an AT91RM9200 we have to setup more than just the SDRAM. Should we put all the init code into cpu/at91rm9200/{start.S} and use CONFIG_ and CFG_? Or should every AT91 based board copy the same code again and again into thier own subdirectory?
Looking forward to your ideas!
Thanks. And sorry for the long mail!
-- Steven Scholz
imc Measurement & Control imc Meßsysteme GmbH Voltastr. 5 Voltastr. 5 13355 Berlin 13355 Berlin Germany Deutschland fon: +49 30 467090-0 Tel: 030 / 467090-0 fax: +49 30 4631576 fax: 030 / 4631576