Re: [PATCH 2/6] PowerPC 440EPx: Sequoia DTS

[Segher Boessenkool <segher@kernel.crashing.org>]

>> address-permutation = <0 1 3 2 4 5 7 6 e f d c a b 9 8>;
>
> Yes, I was contemplating something like that.

Let's not define this until we need it though :-)

>> I haven't heard or thought of anything better either.  Using "ranges"
>> is conceptually wrong, even ignoring the technical problems that come
>> with it.
>
> Why is "ranges" conceptually wrong?

The flash partitions aren't separate devices sitting on a
"flash bus", they are "sub-devices" of their parent.

> To be honest this looks rather to me like another case where having
> overlapping 'reg' and 'ranges' would actually make sense.

It never makes sense.  You should give the "master" device
the full "reg" range it covers, and have it define its own
address space; "sub-devices" can carve out their little hunk
from that.  You don't want more than one device owning the
same address range in the same address space.


Segher