[RFC PATCH 03/19] powerpc: gamecube: bootwrapper bits

[Segher Boessenkool]

>>>> WIMG=0000, are you sure?  Not M=1?
>>>
>>> To be honest, I don't recall the details now.
>>> But it was tested in the very early days, the result was not the
>>> expected one and, in the end, manual cache coherency management was
>>> still needed.
>>
>> Sure, the memory controllers don't do coherency.  I'm slightly worried
>> about two things:
>> 1) Will the generic code use M=0 as well?  Is it a problem if it
>> doesn't?
>> 2) Do lwarx. etc. work in M=0?
>>
>> And a question: does M=0 actually give better performance (lower bus
>> utilisation, and maybe saves a few cycles)?
>
> I think that the generic code uses M=0 _except_ for SMP and some platforms
> (see comment in cputable.h).
> And yes, the generic code works with these processors :)

I meant, if it doesn't, does it give conflicts.  But I did some
reading up and M=0 is indeed the way to go, so all is fine :-)

> M=0 should have a lower bus utilization, yes.
> Also M=0 is a requirement if you use some Gekko/Broadway features like the
> locked (half-)cache.

Well we don't use that, but point taken.


Segher