On Friday 21 March 2014, Rob Herring wrote:

From: Rob Herring <robh@kernel.org>

This started out as an attempt to add arm64's earlyprintk support to ARM
in order to get an earlier, runtime setup console on multi-platform
kernels. The first issue was needing the fixmap support which
conveniently Mark Salter was working on and is mostly in place now. Like
many things on ARM and arm64 now, it then became where do I put the now
common, shared code. After digging more into various early console/printk
support, it turns out the 8250_early.c setup code was the best starting
point. 

This is based on Mark Salter's fixmap support currently in linux-next.
This is tested on arm64 and ARM with pl011 and 8250. The ARM support
also requires fixmap and fixed mapping support which are not yet in place.
I have some patches in my tree to support fixmap, but they need some more
work. Fortunately, once fixmap is in place, it is just a Kconfig option
to enable earlycon support on ARM. A git tree is available here[1].

Based on this series, I would like to add support for doing earlycon
setup using DT.

Hi Rob,

I like this series a lot, great work!

I would consider the DT parsing support essential here, we should not
merge the patches until that is done as well, because I don't want
to see users pass earlycon command line options in DT when they can
use the established "linux,stdout-path" property instead. I would
expect that in almost every case in which we are booting using DT
today, we can just use linux,stdout-path to locate the device that
the boot loader has already set up and start usign it.

	Arnd