U-Boot as ARM Coreboot Payload (for Chromebook Duet)

Hello,

Reading https://chromium.googlesource.com/chromiumos/docs/+/master/developer_mode.md, it appears U-Boot should work as an alternate firmware on new ARM Chromebooks.

Trying on my Duet (Kukui/Krane), this doesn't work. Looking at the RW_LEGACY contents, there's basically nothing there from the factory.

I tried "make coreboot_defconfig" from u-boot master, but it looks like this is x86 only.

Any way to get this working on ARM(64)?

Thanks, --Matt