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

[Scott Wood]

On Thu, 2013-08-22 at 12:44 -0500, Stuart Yoder wrote:
> On Thu, Aug 22, 2013 at 11:23 AM, Scott Wood <scottwood at freescale.com> wrote:
> > On Thu, 2013-08-22 at 11:15 -0500, Stuart Yoder wrote:
> >> On Mon, Aug 19, 2013 at 2:59 PM, Scott Wood <scottwood at freescale.com> wrote:
> >> > On Fri, 2013-08-16 at 09:14 -0500, Stuart Yoder wrote:
> >> >> 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.
> 
> $ find arch/arm/boot/dts | wc -l
> 425
> $ find arch/powerpc/boot/dts | wc -l
> 315

My point is this isn't the first device tree to go into U-Boot for ARM.

> >> 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?
> 
> It doesn't make sense to me to keep one device tree in u-boot
> and the rest in the kernel.

That's not what's being proposed.

> > 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.
> 
> You shouldn't need device trees for building u-boot or the kernel.

Then why mess around with submodules instead of just a separate
repository?

> I don't think a couple of extra commands is that burdensome.

I disagree, and at the least don't want to be the one to advocate such a
change. :-)

> I agree the DTS files really don't belong in the kernel, but there is
> currently no better repository that has been proposed.   I'm not
> sure u-boot is a better place.    Device trees should be independent
> of any particular bootloader or OS.

The final device tree that the OS sees should be independent of the OS.
The dts is not the final device tree, and is tied to U-Boot.  The device
tree in general is also tied to the bootloader in other ways -- U-Boot
expects certain aliases, configurable addresses must match, etc.

-Scott