[PATCH v2 6/7] arm: dts: apple: Add preliminary device trees

[Simon Glass]

Hi Rob,

On Mon, 11 Oct 2021 at 12:36, Rob Herring <robh at kernel.org> wrote:
>
> On Sun, Oct 3, 2021 at 1:35 PM Mark Kettenis <kettenis at openbsd.org> wrote:
> >
> > Add preliminary device trees for the Apple M1 mini (2020) and
> > Apple M1 Macbook Pro 13" (2020).  Device tree bindings for
> > the Apple M1 SoC are still being formalized and these device
> > trees will be synchronized with the Linux kernel as needed.
>
> So not synchronized currently? If it is sync'ed, you should specify
> which version you got.
>
> > These device trees are provided as a reference only as U-Boot
> > uses the device tree passed by the m1n1 bootloader.
>
> If reference only, why do they need to be checked in here? We're
> trying to get to fewer copies both of dtbs at runtime and dts files in
> source trees.
>
> I mainly bring it up here because this is a platform with multiple OS
> targets, following the model that DT comes from the firmware, and
> should be free of schema validation warnings. In other words, it's a
> good candidate to define best practices.

This is something I have brought in, as U-Boot DT maintainer, to
provide some sort of reference in U-Boot as to what is actually built.
It allows people to see the devices and also ensures that the build
system does build a devicetree. The existing OF_PRIOR_STAGE is being
removed and OF_BOARD is becoming a bool, with OF_SEPARATE the standard
approach.

We have a few examples where this is not done (e.g. qemu-arm) but I am
working on fixing that. It has led to discussions about whether U-Boot
is entitled to having its own things in the DT, etc. etc. The whole
area is in flux at present. If you want some background:

https://patchwork.ozlabs.org/project/uboot/patch/20210919215111.3830278-3-sjg@chromium.org/

Regards,
Simon