[PATCH 00/12] Fixing TI Keystone2 kexec

Russell King - ARM Linux linux at armlinux.org.uk
Wed May 11 01:52:03 PDT 2016

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:
> > 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.

RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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