This implementation doesn't have any major deviations from the other EFI
ports. I've copied the boilerplate from arm and arm64.
I've tested this with the following boot flows:
OpenSBI (M-mode) -> u-boot (S-mode) -> loader.efi -> FreeBSD
OpenSBI (M-mode) -> u-boot (S-mode) -> boot1.efi -> loader.efi -> FreeBSD
Due to the way that u-boot handles secondary CPUs, OpenSBI >= v0.7 is required,
as the HSM extension is needed to bring them up explicitly. Because of this,
using BBL as the SBI implementation will not be possible. Additionally, there
are a few recent u-boot changes that are required as well, all of which will be
present in the upcoming v2020.07 release.
Looks good: emaste
Differential Revision: https://reviews.freebsd.org/D25135
2192efc03b