incompatible device trees between u-boot and linux

[Tom Rini]

On Wed, Aug 25, 2021 at 03:58:10PM +0200, Michael Walle wrote:

> Hi,
> 
> I noticed that there is a fallback to the u-boot device tree for linux
> (esp. EFI boot) if no other device tree was found, see [1]. It seems this
> is working fine for imx devices, for example, where you can just boot a
> stock installer iso via EFI. It will just work and it is quite a nice
> feature as a fallback.
> 
> Now for the layerscape architecture, the ls1028a in my case, things are
> more difficult because the bindings differ between u-boot and linux - one
> which comes to mind is DSA and ethernet.
> 
> Which begs the general question, is it encouraged to have both bindings
> diverge? To me it seems, that most bindings in u-boot are ad-hoc and there
> is no real review or alignment but just added as needed, which is ok if
> they are local to u-boot. But since they are nowadays passed to linux
> (by default!) I'm not so sure anymore.
> 
> OTOH The whole structure around a .dts{,i} and -u-boot.dtsi looks like
> they should (could?) be shared between linux and u-boot.
> 
> -michael
> 
> [1]
> https://elixir.bootlin.com/u-boot/v2021.10-rc2/source/common/board_r.c#L471

The U-Boot device tree is supposed to be able to be passed on to Linux
and Just Work.  The bindings are not supposed to be different between
the two (except for when we take the binding while it's being hashed out
upstream BUT THEN RESYNCED).  Incompatible device trees / bindings are a
bug that needs to be fixed.

-- 
Tom
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