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

From: Simon Glass <sjg@chromium.org>
To: Tom Rini <trini@konsulko.com>
Cc: "François Ozog" <francois.ozog@linaro.org>,
	"Albert Aribaud" <albert.u.boot@aribaud.net>,
	"Heinrich Schuchardt" <xypron.glpk@gmx.de>,
	"Ilias Apalodimas" <ilias.apalodimas@linaro.org>,
	"Mark Kettenis" <mark.kettenis@xs4all.nl>,
	"Peter Maydell" <peter.maydell@linaro.org>,
	"QEMU Developers" <qemu-devel@nongnu.org>,
	"Sean Anderson" <seanga2@gmail.com>,
	"Tuomas Tynkkynen" <tuomas.tynkkynen@iki.fi>,
	"U-Boot Mailing List" <u-boot@lists.denx.de>
Subject: Re: [PATCH v5 06/26] arm: qemu: Add a devicetree file for qemu_arm64
Date: Tue, 2 Nov 2021 19:32:54 -0600	[thread overview]
Message-ID: <CAPnjgZ1KYRY9a-WBeHVX-5r2O-KBNVU1-6wHRw1of0qHrCt4yA@mail.gmail.com> (raw)
In-Reply-To: <20211102165718.GR24579@bill-the-cat>

Hi Tom,

On Tue, 2 Nov 2021 at 10:57, Tom Rini <trini@konsulko.com> wrote:
>
> 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.

But that board:

- uses OF_EMBED, which it should not
- does not use SPL, which I need

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

Aren't we all...I can't even keep up with these threads.

Regards,
Simon