Single device tree blob between linux and u-boot

[Maxim Sloyko]

On Thu, Oct 13, 2016 at 11:20 AM, Xo Wang <xow at google.com> wrote:

> Hi folks,
>
> I saw Cedric had mentioned "...you can use the linux compiled [dtb]
> and dd it at the end of the u-boot
> partition..."
>
> To provide the device tree to u-boot, should we do what Cedric said
> and also pass the address of the DTB from U-Boot to Linux? According
> to these slides:
>
> https://events.linuxfoundation.org/sites/events/files/slides/petazzoni-
> device-tree-dummies.pdf
>
> U-Boot can pass the DTB address to Linux in r2 (p. 6) with the right
> bootm command parameters.
>
> This means we can have U-Boot and Linux use the same DTB binary (I
> prefer built in Linux) rather than each source tree building one.
>

This introduces the dependency of U-Boot on Linux. Do we plan to keep this
dependency forever? This may be fine with OpenBMC, but what about mainline
U-Boot and Linux?
Also, are we sure that they are 100% compatible? IIRC Peter was saying that
in practice you need two different device trees for U-Boot and Linux.


>
> Then we can remove the CONFIG_ARM_APPENDED_DTB option in our Linux
> build that is described as a legacy "compatibility" mechanism. We also
> avoid having an extra copy of the DTSs in U-Boot source and avoid
> duplicate DTBs in our image.
>
> Thoughts?
>
> cheers
> xo
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>



-- 
*M*axim *S*loyko
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