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

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 :

quoted

On Sat, Jun 5, 2021 at 8:37 AM Alex Ghiti [off-list ref] wrote:

quoted

Le 4/06/2021 à 15:08, Arnd Bergmann a écrit :

quoted

On Fri, Jun 4, 2021 at 2:06 PM Alexandre Ghiti [off-list ref] wrote:

quoted

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.