[U-Boot] Got u-boot-2012.10 running on at91rm9200 - but why does it work?

[Jens Scharsig]

Hello Arvid,
>>>
>>
>> you don't need change start.s to boot from NOR.
>> If shold set the  #define CONFIG_SYS_TEXT_BASE  0x00000000
> 
> But that's just the thing, I *do* need this change for the board to boot. 
> CONFIG_SYS_TEXT_BASE is 0x10000000 (this is the base address for the flash 
> memory).

YES and NO:
The nor is physical mapped to 0x1000000 that's right.
But during boot from nor the Memory is also mapped to address 0x0.
U-Boot is relocate to ram after ram init. The calculations of the reclocation
process are based on "delta between PC and CONFIG_SYS_TEXT_BASE".

> 
> Without my patch above, I only get this:
> 
> ----------
> U-Boot 2012.10 (Oct 09 2013 - 02:28:44)
> 
> DRAM:  64 MiB
> ----------
> 

So at this position u-boot try to jump to a wrong address or code in ram.

> I thought this was a known problem with at91rm9200 booting from NOR flash?
> There's at least one other board that I know of with the same problem (the 
> Artila Matrix-500).
> 
> 
>> Please see the configuration for eb_cpux9k2 board. This board does boot
>> from NOR with u-boot 2012.10.
> 
> Hmm, you are right. This config does boot my card (after I modify it to suit,
> of course). Besides the different CONFIG_SYS_TEXT_BASE, I think the main 
> differences to the at91rm9200ek config that I based my earlier config on are 
> these things:
> 
> #define CONFIG_SYS_BOOT_SIZE		0x00 /* 0 KBytes */
> #define CONFIG_SYS_U_BOOT_BASE		PHYS_FLASH_1
> #define CONFIG_SYS_U_BOOT_SIZE		0x60000 /* 384 KBytes */
> 
> None of these are declared in the at91rm9200ek config.

This are old items, which needs a clean up.
> 
Regards Jens