linux-kernel - Re: [PATCH] arm64: Print DT machine model in setup_machine

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Message-ID: <20170428165232.GZ13675@arm.com>
Date:   Fri, 28 Apr 2017 17:52:32 +0100
From:   Will Deacon <will.deacon@....com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Geert Uytterhoeven <geert+renesas@...der.be>,
        Catalin Marinas <catalin.marinas@....com>,
        Kevin Hilman <khilman@...nel.org>,
        Mark Brown <broonie@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arm64: Print DT machine model in setup_machine_fdt()

On Fri, Apr 28, 2017 at 06:16:46PM +0200, Geert Uytterhoeven wrote:
> On Fri, Apr 28, 2017 at 4:57 PM, Will Deacon <will.deacon@....com> wrote:
> > On Thu, Apr 27, 2017 at 02:33:05PM +0200, Geert Uytterhoeven wrote:
> >> On arm32, the machine model specified in the device tree is printed
> >> during boot-up, courtesy of of_flat_dt_match_machine().
> >>
> >> On arm64, of_flat_dt_match_machine() is not called, and the machine
> >> model information is not available from the kernel log.
> >>
> >> Print the machine model to make it easier to derive the machine model
> >> from an arbitrary kernel boot log.
> >>
> >> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
> >> ---
> >> I have scripts to save kernel boot logs, and compare logs[*] for
> >> subsequent boots on the same machine.  Having a way to extract the
> >> machine model from an arbitrary kernel boot log makes this easier.
> 
> > I think your use-case is slightly questionable (e.g. for ACPI, we print
> > something different, and this isn't generally considered to be ABI), but
> > the patch is harmless and if you find it useful then:
> 
> Not having access to an ARM ACPI system, what does it print for example?

It's supposed to print out some stuff from DMI, but my Juno just says:

  DMI not present or invalid.

Luckily, it's not really an issue because I don't get to a prompt after USB
fails to come up and it times out mounting the rootfs.

Will