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From:   Grant Likely <grant.likely@secretlab.ca>
Date:   Wed, 5 Sep 2018 19:00:33 +0100
Message-ID: <CACxGe6tbuDzEaBqOD7Z3nWMW0Nkcf22MFbD3BL+KBqnKEo2tQw@mail.gmail.com>
Subject: Re: [PATCH] arm64: defconfig: enable EFI_ARMSTUB_DTB_LOADER
To:     scott.branden@broadcom.com
Cc:     Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Olof Johansson <olof@lixom.net>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Arnd Bergmann <arnd@arndb.de>,
        bcm-kernel-feedback-list@broadcom.com,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Leif Lindholm <leif.lindholm@linaro.org>,
        Alexander Graf <agraf@suse.de>
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On Wed, Sep 5, 2018 at 6:27 PM Scott Branden <scott.branden@broadcom.com> wrote:
>
>
>
> On 18-09-05 02:40 AM, Ard Biesheuvel wrote:
> > On 4 September 2018 at 19:19, Scott Branden <scott.branden@broadcom.com> wrote:
> >> Rather than introduce EFI_ARMSTUB_DTB_LOADER, why not have
> >> the efistub use CONFIG_OF to determine whether it supports dtb= or not?
> >>
> >> That way ACPI-only distros disable devicetree support entirely.
> >>
> > Unfortunately, CONFIG_OF cannot be disabled on arm64 even on ACPI-only builds.
> OF shouldn't be automatically selected in the arm64/Kconfig.  It should
> have a config
> parmaeter like other archs as mips and arm.  I can submit a patch so it
> functions the
> same way as other archs so it is not always selected.  It will be good
> to add a USE_OF
> config options like the other archs (or simply remove the select from
> the Kconfig and choose OF directly in the defconfig.
> This will have the added benefit of doing away with OF support when its
> not needed on an ARM64 platform.  ACPI is already not automatically
> selected for all ARM64 platforms, nor should devicetree.

We don't do that on Arm because a devicetree is always required at
boot time. Even on ACPI systems a tiny DTB is used containing just a
/chosen node for passing the kernel command line and the initrd
location.

g.

g.