quoted

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