[U-Boot] arch/powerpc/lib/board.c:get_effective_memsize() for 4GB+ systems

Tabi Timur-B04825
2012-09-20T22:37:40Z

On Thu, Sep 20, 2012 at 3:24 PM, Robert Thorhuus
<robert.thorhuus@ericsson.com> wrote:

> I'm using 64 bit mpc85xx cores.

U-Boot runs in 32-bit mode even on a 64-bit code.

> Mapping the whole memory from the beginning was of course just an initial thought.
> But for me it looks like the code is just not able to deal with more than 3.99GB mapped. U-Boot will not be able to be relocated.

I would be very surprised if U-Boot could handle a value of
CONFIG_MAX_MEM_MAPPED larger than 2GB, no matter what. We use the
address space above 2GB for I/O addresses, like CCSR and PCI memory.
You would need to reshuffle your I/O memory mappings to use a larger
value. And even then, we've never tested that, and so who knows what
obscure bugs are in the code.

Is there a reason why you need access to more than 2GB of RAM from
within U-Boot?

--
Timur Tabi
Linux kernel developer at Freescale