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

[Tom Rini]

On Mon, Oct 11, 2021 at 02:00:56PM -0600, Simon Glass wrote:
> Hi Rob,
> 
> On Mon, 11 Oct 2021 at 13:49, Rob Herring <robh at kernel.org> wrote:
> >
> > On Mon, Oct 11, 2021 at 2:00 PM Mark Kettenis <mark.kettenis at xs4all.nl> wrote:
> > >
> > > > From: Rob Herring <robh at kernel.org>
> > > > Date: Mon, 11 Oct 2021 13:36:29 -0500
> > >
> > > Hi Rob,
> > >
> > > > 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.
> > >
> > > Not synched at the moment.  It is based on what was in 5.13 or 5.14,
> > > but with lots of stuff added so specifying a version would be
> > > misleading.  It should be mostly aligned with the bindings that are
> > > making their way into 5.15 or 5.16 though.
> >
> > This and what's added or preliminary would be good to have in the commit msg.
> >
> > > Hopefully now that the power domains are getting addressed we'll have
> > > something that can be synchronized soon.  I was explicitly encouraged
> > > to start upstreaming the U-Boot code even though not all the DT
> > > bindings had been sorted out.
> >
> > In general, sounds like a recipe for getting out of sync and bindings
> > never getting documented properly without any checks in place. The
> > good news is checking that is at least possible now.
> >
> > > > > 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.
> > >
> > > The U-Boot maintainers insist there is a DT for each supported system
> > > in the U-Boot tree.
> >
> > Ok, fair enough.
> >
> > > > 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.
> > >
> > > You're preaching to the choir ;).
> >
> > Good.
> >
> > > Must admit that it is somewhat convenient for me to have a somewhat
> > > complete DT for these devices at the moment.  But in the long run I
> > > think it will just confuse people.  That said, I plan to be aggressive
> > > in keeping the U-Boot tree synchronized with Linux.
> >
> > What I'd like to see here is some sort of automatic synchronization.
> > The idea I have here is just a list of boards to sync from the kernel
> > tree to wherever. The requirement to get on the list would be passing
> > schema validation and would be a declaration of stability (there's
> > been numerous discussions over the years of how to declare a DT stable
> > or unstable). It would perhaps also include passing validation on an
> > older schema. I'm not sure how well that would catch compatibility
> > issues, but that's the only idea I've come up with besides just
> > testing of mixed versions. I'm happy to do the tooling to support that
> > if we have a board/device to put in the list and u-boot folks agree to
> > use it. I suppose even if just m1n1 used it to start with, I'd be
> > willing to do the tooling.
> 
> That sounds great to me. Yes m1n1 is a good first target since it is
> new, but I'm pretty sure there are quite a few other SoCs that could
> move over right away.
> 
> Ideally we would add it to U-Boot CI too, so that pull requests warn
> or fail if something wrong is added. Of course it is probably a no-no
> to make U-Boot CI due to comparisons with another tree over which we
> have no control, but perhaps we can head in that direction.
> 
> +Tom Rini too as he has been looking at this.

I guess the first priority is that so long as _everything_ is in sync,
it doesn't super matter if we have an otherwise redundant copy of files
in-tree.

And we need to get our DTS files back in sync with upstream, which is
the case for some platforms, and not others.  But once we get that
sorted out, we need to do more regular resyncs, and hopefully once
DTS files have settled down, because they all pass validation and for
example incorrect names get fixed, it will be less of an issue to more
automatically resync DTS files, that are fully validated at least.

-- 
Tom
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