[U-Boot] [PATCH v3 2/5] board support of arm64

[Scott Wood <scottwood@freescale.com>]

On Thu, 2013-08-22 at 11:15 -0500, Stuart Yoder wrote:
> On Mon, Aug 19, 2013 at 2:59 PM, Scott Wood <scottwood@freescale.com> wrote:
> > On Fri, 2013-08-16 at 09:14 -0500, Stuart Yoder wrote:
> >> On Thu, Aug 15, 2013 at 8:47 AM,  <fenghua@phytium.com.cn> wrote:
> >> > From: David Feng <fenghua@phytium.com.cn>
> >> >
> >> > This patch provide u-boot with arm64 support. Currently, it works on
> >> > Foundation Model for armv8 or Fast Model for armv8.
> >> >
> >> > Signed-off-by: David Feng <fenghua@phytium.com.cn>
> >> > ---
> >> > Changes for v3:
> >> >     - rewrite cache.S and exception.S that partly originated from linux kernel,
> >> >       so the license should be ok.
> >> >
> >> >  board/armltd/dts/vexpress64.dts      |  215 ++++++++++++++++++++++++++++++++++
> >>
> >> Why is the device tree source in u-boot (instead of in the kernel)?
> >> Is this temporary?   It
> >> looks like this device tree is just a copy from somewhere else.
> >>
> >> Would suggest removing this from this patch series and keep the dts maintained
> >> in the Linux kernel.
> >
> > U-Boot itself uses the device tree (not just to patch up for Linux) on
> > some targets.
> >
> > Even with the way PPC uses device trees, it doesn't really make sense to
> > keep them in the kernel given that they're meant to be OS-neutral, and
> > have ties to U-Boot in terms of what gets fixed up at runtime.
> 
> It may not make sense, but that is where they are kept currently. 

For PPC.

> It doesn't make sense to maintain 2 copies of a vexpress64.dts device tree in 2 different
> places...or to maintain 1 lone device tree in u-boot.

Why does it not make sense for there to be one lone device tree in
U-Boot?

A device tree that is not used with U-Boot may not look the same, since
U-Boot is (at least on some platforms) responsible for filling in parts
of the tree, and (again on some platforms) for setting up the address
map.

> Maybe we need a git repo for device trees that could be included
> in Linux, u-boot, and other things a submodule.

Submodules can be a pain.  If we don't use them for DTC, why would we
use them for this?  Since they require extra commands, you'd be
modifying the workflow of everyone that builds U-Boot and/or Linux for
affected platforms.

-Scott