Re: [PATCH 1/6] arm64: Unconditionally call unflatten_device_tree()

Hi Mark,

On Thu, Jan 18, 2024 at 4:27 PM Mark Rutland [off-list ref] wrote:

On Tue, Jan 16, 2024 at 05:27:18PM -0800, Stephen Boyd wrote:

quoted

Quoting Mark Rutland (2024-01-16 03:51:14)

quoted

On Fri, Jan 12, 2024 at 12:07:44PM -0800, Stephen Boyd wrote:

quoted

Call this function unconditionally so that we can populate an empty DTB
on platforms that don't boot with a firmware provided or builtin DTB.
There's no harm in calling unflatten_device_tree() unconditionally.

For better or worse, that's not true: there are systems the provide both a DTB
*and* ACPI tables, and we must not consume both at the same time as those can
clash and cause all sorts of problems. In addition, we don't want people being
"clever" and describing disparate portions of their system in ACPI and DT.

It is a very deliberate choice to not unflatten the DTB when ACPI is in use,
and I don't think we want to reopen this can of worms.

Hmm ok. I missed this part. Can we knock out the initial_boot_params in
this case so that we don't unflatten a DTB when ACPI is in use?

Why is that better than just not calling unflatten_device_tree(), as we do
today?

The cover letter says this is all so that we can run DT tests for the clk
framework; why can't that just depend on the system being booted with DT rather
than ACPI? We have other tests which are architecture and/or configuration
dependent...

There is definitely a merit in running (platform-independent) DT tests
on any platform, whether the platform actually uses DT to boot or not.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

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