Adding EFI runtime support to the Arm's FF-A bus

[Abdellatif El Khlifi]

Hi guys,

I'd like to ask for advice regarding adding EFI RT support to the Arm's FF-A bus
in U-Boot.

The objective is to enable the FF-A messaging APIs in EFI RT to be used for
comms with the secure world. This will help getting/setting EFI variables
through FF-A.

The existing FF-A APIs in U-Boot call the DM APIs (which are not available at RT).

Two possible solutions:

1/ having the entire U-Boot in RT space (as Simon stated in this discussion[1])

2/ Create an RT variant for the FF-A APIs needed.
      These RT variant don't call the DM APIs
      (e.g: ffa_mm_communicate_runtime, ffa_sync_send_receive_runtime, ...)

What do you recommend please ?

[1]: https://lore.kernel.org/all/CAPnjgZ21qLnSFcCJ9rPQXEfQf-NjMBF3kYUDBBOc6WUQXQtDEA@mail.gmail.com/

Cheers,
Abdellatif