Re: [PATCH v5 06/26] arm: qemu: Add a devicetree file for qemu_arm64

[Tom Rini]

On Tue, Nov 02, 2021 at 08:59:45AM -0600, Simon Glass wrote:
> Hi François,
> 
> On Mon, 1 Nov 2021 at 11:33, François Ozog <francois.ozog@linaro.org> wrote:
> >
> > Hi Simon
> >
> > Le lun. 1 nov. 2021 à 17:58, Simon Glass <sjg@chromium.org> a écrit :
> >>
> >> Hi Peter,
> >>
> >> On Mon, 1 Nov 2021 at 04:48, Peter Maydell <peter.maydell@linaro.org> 
> >> wrote:
> >> >
> >> > On Tue, 26 Oct 2021 at 01:33, Simon Glass <sjg@chromium.org> wrote:
> >> > >
> >> > > Add this file, generated from qemu, so there is a reference devicetree
> >> > > in the U-Boot tree.
> >> > >
> >> > > Signed-off-by: Simon Glass <sjg@chromium.org>
> >> >
> >> > Note that the dtb you get from QEMU is only guaranteed to work if:
> >> >  1) you run it on the exact same QEMU version you generated it with
> >> >  2) you pass QEMU the exact same command line arguments you used
> >> >     when you generated it
> >>
> >> Yes, I certainly understand that. In general this is not safe, but in
> >> practice it works well enough for development and CI.
> >
> > You recognize that you hijack a product directory with development hack 
> > facility. There is a test directory to keep things clear. There can be a 
> > dev-dts or something similar for Dev time tools.
> > I have only seen push back on those fake dts files in the dts directory: I 
> > guess that unless someone strongly favors a continuation of the discussion, 
> > you may consider re-shaping the proposal to address concerns.
> 
> As stated previously, I would like to have at least a sample DT
> in-tree for all boards. I cannot see another way to get the Kconfig

What's the point of having a sample when it's not going to always be
correct or may be actively wrong and we can tell interested developers /
users how to get the correct DTB/DTS to examine?

> options in line. If we are able to put these files somewhere else in
> the future and get them out of U-Boot, with perhaps just an overlay
> for development purposes, I'd be keen to see it. But for now, this is
> where we are, I believe.
> 
> In this particular case, this is not just a dev hack. It is also for
> CI tests which need to use a devicetree. See for example here:
> 
> https://patchwork.ozlabs.org/project/uboot/patch/20211101011734.1614781-15-sjg@chromium.org/
> https://patchwork.ozlabs.org/project/uboot/patch/20211101011734.1614781-24-sjg@chromium.org/

This example would probably be better done on vexpress_ca9x4 where we do
test in CI via QEMU but do not need to modify a device tree that is
passed on to us, we already control the source of truth DTB in this
case.

And also yes, I'm behind on reviewing things I need to review.

-- 
Tom

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