are there PHYS_OFFSET alignment requirements for ARM Linux?
Nicolas Pitre
nico at fluxnic.net
Thu Jul 19 15:07:42 EDT 2012
On Wed, 18 Jul 2012, John Linn wrote:
> I have seen some mention of 2 MB alignment requirements, but it's not
> clear to me if that's true or not (looks old)?
>
> My apologies if it's obvious somewhere, but are there any alignment
> requirements?
There is a 2MB alignment requirement on PHYS_OFFSET. You may play
tricks with memory reservation if a smaller offset is required, but I'd
recommend against that. Even 2MB is too small an alignment if you want
to have CONFIG_ARM_PATCH_PHYS_VIRT=y (the default) which requires a 16MB
alignment.
It is very exceptional to see systems where RAM is not aligned to a much
bigger boundary. Why would you need a 2MB alignment?
Nicolas
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