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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Sat, 5 Jun 2021 13:00:42 +0200
Message-ID: <CAK8P3a1_N6dAdjWR10FtgaVz828o7W5Mp55DO3Ex+3en-ikOUw@mail.gmail.com>
Subject: Re: [PATCH -fixes] riscv: Fix BUILTIN_DTB for sifive and microchip soc
To:     Alex Ghiti <alex@ghiti.fr>
Cc:     Rob Herring <robh+dt@kernel.org>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        DTML <devicetree@vger.kernel.org>,
        linux-riscv <linux-riscv@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Sat, Jun 5, 2021 at 8:37 AM Alex Ghiti <alex@ghiti.fr> wrote:
> Le 4/06/2021 à 15:08, Arnd Bergmann a écrit :
> > On Fri, Jun 4, 2021 at 2:06 PM Alexandre Ghiti <alex@ghiti.fr> wrote:
> >>
> >> Fix BUILTIN_DTB config which resulted in a dtb that was actually not built
> >> into the Linux image: in the same manner as Canaan soc does, create an object
> >> file from the dtb file that will get linked into the Linux image.
> >>
> >> Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
> >
> > Along the same lines as the comment that Jisheng Zhang made on the fixed
> > address, building a dtb into the kernel itself fundamentally breaks generic
> > kernel images.
> >
> > I can understand using it on K210, which is extremely limited and wouldn't
> > run a generic kernel anyway, but for normal platforms like microchip and
> > sifive, it would be better to disallow CONFIG_BUILTIN_DTB in Kconfig
> > and require a non-broken boot loader.
>
> I kind of disagree because if I want to build a custom kernel for those
> platforms with a builtin dtb for some reasons (debug, development..Etc),
> I think I should be able to do so.

How is the builtin dtb better than appended dtb, or passing the dtb to the
boot loader in that case?

         Arnd