On Wed, May 11, 2016 at 04:29:23PM +0800, Dave Young wrote:

Hi, Russell

On 04/28/16 at 10:26am, Russell King - ARM Linux wrote:

quoted

These changes are required for TI Keystone2 kexec to be functional.  TI
Keystone2 has the run-time view of physical memory above 4GiB, but with
a boot time alias below 4GiB which can only be used during the early
boot.

This means we need to translate run-time physical addresses (which the
kernel uses) to boot-time physical addresses, which, having discussed
with Eric, is what the kexec tools and kexec kernel API requires.

We publish a special set of boot time resources in /proc/iomem, which
the (modified) kexec tools look for in preference to the normal resources.
Hence, if these are found, the kexec tools make use of these resources,
and thus kexec tools use the boot-time view of physical memory.

I think getting memory ranges from device tree will be better than
adding more stuff to /proc/iomem. Geoff's arm64 kexec patches is using dtb
you can refer to the patchset.

I think you're confusing things.  DT doesn't contain the boot alias
memory ranges - it's not a separate chunk of memory.  It's an alias
of the same physical address space found higher in the physical
address range.

If we put it in DT, then we need a way to also describe that it is an
alias of some other bit of physical memory.

-- 
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