[U-Boot] [PATCH] image: check "bootm_low" and "bootm_size" if "initrd_high" is missing

[Masahiro Yamada]

Hi Tom,


2016-01-05 4:59 GMT+09:00 Tom Rini <trini at konsulko.com>:
> On Thu, Dec 17, 2015 at 05:19:35PM +0900, Masahiro Yamada wrote:
>
>> To boot Linux, we should prevent Initramdisk and FDT from going too
>> high.
>
> OK, why?  I could be entirely wrong here but I had thought for some
> reason that if the ramdisk was in "highmem" the kernel would relocate
> contents (or if compressed, uncompress to a non-highmem location).  The
> FDT must be in lowmem as that tells the kernel where memory even is.  Is
> this not the case?  Thanks!


Just in case, I asked this in the kernel ML.


See this thread:
https://lkml.org/lkml/2016/1/8/169


Jon gave me the answer.



5. Load initramfs.
------------------

Existing boot loaders:          OPTIONAL
New boot loaders:               OPTIONAL

If an initramfs is in use then, as with the dtb, it must be placed in
a region of memory where the kernel decompressor will not overwrite it
while also with the region which will be covered by the kernel's
low-memory mapping.

A safe location is just above the device tree blob which itself will
be loaded just above the 128MiB boundary from the start of RAM as
recommended above.





-- 
Best Regards
Masahiro Yamada