[PATCH] Start arch/powerpc/boot code reorganization

Segher Boessenkool segher at kernel.crashing.org
Fri Sep 22 01:31:18 EST 2006

> On PPC44x (and other PowerPC processors) the number of address cells
> to represent a virtual address and a physical address differ due the
> 36-bits of physical address space.

The number of virtual address cells is always 1.  A cell isn't always
32-bits though.  Want more confusion?  Lots of properties are called
"<something>-cells" etc., but those names are historical; the proper
name for the things encoded in properties is "32-bit integers".

> Regardless of the name of the
> new property, it should be defined to allow a different number of
> address cells to represent an address in virtual address space.

How about you check whether the "64-bit" property exists in the CPU

>> (*)  This isn't strictly correct, but OF doesn't describe the size of
>> virtual addresses anywhere.  In practice, it's the same as the size
>> of physical addresses always.  Oh, and the name "virtual" isn't  
>> correct
>> in PowerPC-speak anyway, heh.
> Actually, in practice, it's not always the same size as a physical
> address. We have 36-bit physical addressing systems in the real world.

Darn, and you have #address-cells = 2 in the root node?  It's allowed,

> FWIW, I'd be happy with this property name or fw,address. When we
> discussed this on IRC the thought was to conform to what already
> existed for this purpose in the OF spec. Since the address prop sounds
> like it will confuse some people I think it makes sense to add a
> new property (might as well just throw out the spec :P).

But if you do make something new, you'll have to make it better
than what you're replacing, or what's the point :-)


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