kexec on e300 core / mpc5121

[Kumar Gala]

On Aug 5, 2009, at 5:49 PM, Kenneth Johansson wrote:

> On Wed, 2009-08-05 at 01:06 +0200, Sebastian Andrzej Siewior wrote:
>> I've tried kexec on e300 core which should be easy since it is  
>> possible
>> to disable the MMU on that core. However it does not work.
>
> Is it not possible to disable the mmu on all cpu's that have one ??

Nope.  Book-E class PPC parts always have the mmu.

>> Once I disable the MMU, I can't access my MBAR and print chars on the
>> serial port. Is this "normal" or do I have still some caches on?
>
> Yes cache and mmu is separate. the 5121 is not cache coherent and do  
> not
> limit cache to only memory regions so serial port or any memory mapped
> register is a no no unless you have cache off or cache on and mmu on
> with a correct setting for what address range to cache.
>
> Before you turn off the cache you need to flush out all dirty data.  
> best
> done by simply reading in 32kb of crap from somewhere. otherwise you  
> are
> sure to loose at least the stack and you do not want that.

- k