[PATCH 0/8] Generic serial earlycon

On Sunday 23 March 2014, Rob Herring wrote:

IIRC, the unflattening cannot be done before memblock is up which is
in arm_memblock_init. I believe that will get done earlier similar to
PPC with Laura's meminfo removal series. However, in interest of
getting output enabled as early as possible, the earliest point is
always going to be with a flat tree. So I think we do want to be able
to parse the flat tree for this. There's code in u-boot to do the
address translation on FDT we can steal. Really, i'd like to put that
code in libfdt, but there's a licensing problem with the u-boot code
being GPL and libfdt being BSD.

I suppose it depends on what the goal is. If you are trying to get as
close as possible to the debug_ll functionality without losing the
ability to turn it on unconditionally, I agree that it needs to be done
on the flat tree.

However, the goal that interests me more at the moment is to have
reliable debug output done in a simple way earlier than what we have
today with the normal console support. For this, it seems a better
tradeoff to initialize the early console slightly later. This
can actually be done independent of the the command line option,
I don't see any downsides from having a compile-time option that
would initialize the early console from setup_arch (after
unflatten_device_tree) whenever there is a linux,stdout-path
property that points to a usable device.

	Arnd