[U-Boot] Porting to Broadcom BCM7038 (Hermes board)

[Wolfgang Denk]

Dear Peter Belm,

In message <574bb010908200229m7da12930s39f7bc40a2384f1d at mail.gmail.com> you wrote:
>
> > That's not quite correct. IIRC, the "purple" board also uses a 64bit
> > MIPS processor (5Kc). So it's "just" anothe rnew board port.
> 
> The core in the BCM7038 is a 5Kf, I'm not sure how the minor revision
> effects something like UBoot, would any registers be different? As for it

Well, _all_ hardware differences affect U-Boot. You will need a really
detailed understanding of the processor and your board.

> being 64bit, the current bootloader is being compiled with a 32bit version
> of mipsel-uclibc-gcc, so it runs 32bit code fine. Would this be easier, or

Right. That's what we do in case of the "purple" board, too.

> does the fact it's a 64bit processor mean there's other changes which need
> to be taken into account in UBoot?

This obviously depends on your hardware design. We cannot answer this
question.

> Ok I think I get it now, in the cpu directory goes the code specific for
> bringing up the cpu, using the cache, etc. So the board directory would
> contain code for accessing the flash, init'ing memory, etc. And drivers
> would go into drivers/ as you said.

Assuming you use standard flash chips, no code to access the flash
should co to the board directory. You should use the existing standard
drivers instead.

> There's one fundamental thing I still need to get sorted in my head, what
> exactly is the role of UBoot? Is it just there to assist in creating a
> bootloader? So the cpu code would do the main bringup, board specific code

U-Boot _is_ the boot loader.

> would init the memory then use drivers provided by UBoot to access what it
> needs to load the kernel, then calls code in UBoot to start it? Or does
> UBoot perform a more invasive role than that?

All the tasks you mention here are performed by U-Boot. U-Boot _is_
the boot loader.

Best regards,

Wolfgang Denk

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