Subject: Re: [PATCH 10/13] powerpc: check cache coherency of kernel vs firmware

From: Segher Boessenkool <[email-masked]>
Date: Mon, 14 May 2007 14:34:49 +0200

>> check_cache_coherency() verifies that the cache coherency setting of
>> the kernel (CONFIG_NOT_COHERENT_CACHE) matches that left by the 
>> firmware,
>> as indicated by coherency-off device tree property.
>
> This looks really bogus.  If the firmware reports a coherency state,
> then presumably there's some hardware switch to turn coherency on or
> off.  In which case, can't the kernel just toggle that switch to
> whatever's appropriate for it?

But can the kernel know in all cases what is the
appropriate setting?  This kind of thing is a
typical firmware job.

Segher