Boot interface for device trees on ARM
Jeremy Kerr
jeremy.kerr at canonical.com
Wed May 19 04:50:53 EDT 2010
Nicolas,
> Exact. For example, on ARM the machine ID is also used to figure out
> the MMU mapping needed to be able to simply be able to debug the very
> early assembly boot stage when there isn't even a stack available.
I get the impression that this is the only thing that we need the io_pg_offset
for - setting up the debug page mapping, for very early printk output.
If this is the case, I would much rather have it as a compile-time constant
when doing this early debug; this is what I have been doing for DT boot in my
tree (however, I would like to move it to something more configurable).
In the cases where we need to debug the pre-C stuff (ie, machine bringup), I
think we can live with a compile-time constant, rather than having to define a
special 'exception' in the DT boot interface to handle this.
Or is there another early use of the mdesc that I'm not aware of?
Cheers,
Jeremy
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