[U-Boot-Users] TEXT_BASE
Michael Frey
michael.frey at pepper.com
Wed Feb 5 21:25:53 CET 2003
So I am still confused.
My board's flash sits at 0x00000000 this is where I load u-boot.bin and
TEXT_BASE is also the same.
This is also where the cpu jumps to to start executing.
How does u-boot know where to relocate itself to in RAM?
On Tuesday, February 4, 2003, at 05:28 PM, Wolfgang Denk wrote:
> [Let's keep the list Cc:ed or others will ask the same questions
> again later. Well, they will anyhow :-( ]
>
> In message <8C12DADD-388E-11D7-8C12-00039390D626 at pepper.com> you wrote:
>>
>> I am still a bit confused. Should I set TEXT_BASE to 0x0000000
>> because
>> that is where physical flash is located? or somewhere else.
>
> This depends. I don't know which architecture or board you are
> talking about. On PowerPC for example, you will need to have RAM
> mapped to physical address 0x0000 - at least if you ever want to run
> Linux.
>
> The thing is that it is _you_ who defines the physical address map,
> and who programs it with the memory controller of your board. In the
> resulting final mapping, TEXT_BASE is the start address of the U-Boot
> image.
>
> Let's stick with PPCBoot: after reset, a special temporary mapping is
> in place, which will always access memory using /CS0. Note that this
> temporary situation has nothing to do with the value defined for
> TEXT_BASE.
>
> Best regards,
>
> Wolfgang Denk
>
> --
> Software Engineering: Embedded and Realtime Systems, Embedded Linux
> Phone: (+49)-8142-4596-87 Fax: (+49)-8142-4596-88 Email: wd at denx.de
> You know that feeling when you're leaning back on a stool and it
> starts to tip over? Well, that's how I feel all the time.
> - Steven Wright
>
>
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