[RFC PATCHv1 0/7] ARM core support for hardware I/O coherency in non-SMP platforms

Thomas Petazzoni thomas.petazzoni at free-electrons.com
Mon May 19 06:38:15 PDT 2014

Dear Catalin Marinas,

On Wed, 14 May 2014 18:04:56 +0100, Catalin Marinas wrote:

> >    - The pages must be set as shareable.
> Here you may have some conflict between the initial page tables set in
> __create_page_tables as non-shareable (that's unless MPIDR shows it as
> SMP but I guess not since smp-on-up kicks in). I have to think a bit
> more about the implications (the ARM ARM has a chapter on mismatched
> memory attributes and I think it talks about shareable vs
> non-shareable).

Do you have more insights about this potential conflict?

The problem is that at the arch/arm/kernel/head.S stage, it's currently
not possible to do platform-specific code while keeping multiplatform
characteristics, because I don't see how we could get a machine_desc
pointer or any other platform-specific indicator so early in the boot.
Do you have suggestions?


Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering

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