Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Fri, 11 Jun 2021 21:10:45 -0700 (PDT)
Subject:     Re: [PATCH -fixes] riscv: Fix BUILTIN_DTB for sifive and microchip soc
In-Reply-To: <5d3a00d1-9e45-398a-39cf-1e6e9924eb18@ghiti.fr>
CC:     Arnd Bergmann <arnd@arndb.de>, robh+dt@kernel.org,
        Paul Walmsley <paul.walmsley@sifive.com>,
        aou@eecs.berkeley.edu, devicetree@vger.kernel.org,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
From:   Palmer Dabbelt <palmer@dabbelt.com>
To:     alex@ghiti.fr
Message-ID: <mhng-10244c1f-e77f-4b81-80ef-1b6d1a73c095@palmerdabbelt-glaptop>
Mime-Version: 1.0 (MHng)
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: bulk

On Sun, 06 Jun 2021 00:40:34 PDT (-0700), alex@ghiti.fr wrote:
> Le 5/06/2021 à 13:00, Arnd Bergmann a écrit :
>> 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?
>
> Ah never said it was better, just it was available so there is no reason
> we could not allow it :)

I agree: I'm not really a fan of BUILTIN_DTB (and I tried pretty hard 
not to have it in the first place), but whatever we have shouldn't be 
broken.

This is on fixes.