aarch64 startover

[orangecms]

see https://github.com/rust-embedded/aarch64-cpu

Cortex-A has good support in Rust Embedded already. We can build on top of that and port something like a Rockchip or Allwinner ARM SoC. See also #533 and #602.

[orangecms]

see #684 for Allwinner H616

[felipebalbi]

Hi,

I would like to help, where possible, with reworking the AArch64 port. It appears that fixing what currently sits in src.broken is not the way to go. Could we get some better description of what the community is wanting to do for the AArch64 port?

Thanks

[orangecms]

Hi and welcome to the project!

There is not much of an architecture specific goal for oreboot, so it's your chance to contribute and discuss it, if you feel like there is a need. :)

The general idea is to keep things simple and only do as much as necessary to boot up a kernel without any sort of runtime services a fanciness. We leave it up to the OS or bootloader to do more. See also the notes on the boot flow. That usually boils down to some GPIOs, a UART for debugging, DRAM init, loading a kernel to DRAM and jumping to it. Depending on the platform, that may mean some extra code in order to load the kernel from some storage in the first place, e.g., SPI flash, eMMC or SD card.

[felipebalbi]

Here's a first draft for reviving qemu-aarch64: #732