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

[David Long]

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?).  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.

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.

-dl