[U-Boot] [uboot PATCH v2] Add uboot "fdt_high" enviroment variable

[Scott Wood]

On Thu, 14 Jul 2011 16:09:16 -0400
David Long <dave.long at linaro.org> wrote:

> On Thu, 2011-07-14 at 14:43 -0500, Scott Wood wrote:
> 
> 
> > You need to use lmb_reserve() to exclude any memory regions that are not
> > suitable for boot images -- see powerpc's arch_lmb_reserve() and
> > get_effective_memsize()/CONFIG_SYS_LINUX_LOWMEM_MAX_SIZE.
> 
> 
> If one excludes HIGHMEM from the area u-boot is allowed to relocate the
> fdt/initrd to, then it will put it at the end of the 3/4GB boundary (can
> one exclude all memory above the kernel start address?).

You have memory below where the kernel is loaded?

> This splits
> memory into three, instead of two regions in the kernel.  I don't think
> that split ever goes away. Then there's the additional region we already
> have to create for the Ducati memory.   That's at least five memory
> regions total.  There are only eight regions currently allowed by
> default.  I don't have a feel for the implications of this, but it seems
> unnecessary.

What do you mean by a "region" here, and why can there only be eight of
them?

> Again, I don't think the problem is where u-boot relocates this data
> TOO, but the fact that the new default is to relocate it at all.  Is
> there a reason for relocating this stuff?  The initrd always used to be
> happy left where it was.

The user specified address might be in flash.

-Scott