Re: [PATCH 06/11] arm-dt: postpone machine detection until setup_arch with CONFIG_ARM_DEVTREE

[Jeremy Kerr <jeremy.kerr-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>]

Hi Ben,

> > When we're using CONFIG_ARM_DEVTREE, we need to postpone machine
> > detection until later in setup_arch. Because ARM_DEVTREE depends on
> > !DEBUG_LL, we don't need the mdesc this early anyway.
> >
> > We'll add support for ARM_DEVTREE && DEBUG_LL later.
> 
> Why not add a specific machine type for 'this is device tree' and
> then these routines don't even need to #ifdef. It would especially
> be good as it allows dt and non-dt machines to coexist in the same
> kernel together.

Mainly because this doesn't gain us much; the machine_desc that is discovered 
from this new machine type would not have the correct data (phys_io & 
io_pg_offset) required for early setup (used for DEBUG_LL).

We could conditionally skip the detection if we see a DT machine type, but 
then we'd need to add similar checks for all the paths where the machine_desc 
is used.

However, my goal is indeed to allow DT and non-DT machines to coexist as much 
as possible, this patch is more a temporary workaround while I figure out how 
to handle the DEBUG_LL stuff nicely for DT cases.

Cheers,


Jeremy