[PATCH -fixes] riscv: Fix BUILTIN_DTB for sifive and microchip soc

[Palmer Dabbelt]

On Sun, 06 Jun 2021 00:40:34 PDT (-0700), alex at 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 at 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 at 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 at 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.