How to build U-Boot with a custom out-of-tree device tree

[Simon Glass]

Hi Johannes,

On Sun, 19 Apr 2026 at 02:40, Johannes Krottmayer <krotti83 at proton.me> wrote:
>
> Hello,
>
> This question is generic and also valid for none RISC-V boards.
> I think it's maybe already asked, but didn't find any useful
> information this time. My question is, is it possible to pass
> a specific device tree blob to the build system from U-Boot?
>
> Example: RISC-V board Starfive VisionFive 2 8GiB variant
>
> The default in-source-tree device tree from the VisionFive 2 has
> only 4GiB RAM. I own the 8GiB (RAM-IC BiWin BMWZCX32H2A-64G-X)
> variant. So therefore can I pass the device tree blob directly
> to U-Boot's build system without modifying CONFIG_DEFAULT_DEVICE_TREE
> in the device configuration? Exists there an environment variable?
>
> Want to use U-Boot's EFI subsystem as loader for bare-metal
> environments. And I think when I want to get the memory map
> via EFI there will with the default device tree only <4GiB free
> usable memory shown, although there are 8GiB.

You can build with: make DEVICE_TREE=...

See dts/Makefile for the logic.

>
> Thanks in advance!
>
> Kind regards,
>
> Johannes K.

Regards,
Simon