Support generic-timer (and EL2) on Armv7-A

[jonathanpallant]

Fixes #140 by adding generic timer support for Armv7-A.

• Unfortunately this means testing on Cortex-A15, because Cortex-A8 doesn't have the Timer Extension
• Unfortunately Cortex-A15 has virtualisation support and boots at EL2
• So I had to make Armv7-A use the same EL2-capable boot code as Armv8-R
• And that mean moving a bunch of registers out of the registers::armv8r module and into a new registers::hyp module available on Armv7-A and Armv8-R

[jonathanpallant]

rebased on main

[wt]

I think the code changes look fine.

With regard to the cpu switch for qemu, is there no value to keeping the tests on that qemu target so that we have both? I just want to make sure we aren't losing any meaningful test coverage.

[thejpster]

I think the code changes look fine.

With regard to the cpu switch for qemu, is there no value to keeping the tests on that qemu target so that we have both? I just want to make sure we aren't losing any meaningful test coverage.

You mean the switch from Cortex-A8 to Cortex-A15? I don't think the matters - they will use the same emulation engine underneath. I only switched because the A15 has some extra features enabled that we needed.

[wt]

I think the code changes look fine.
With regard to the cpu switch for qemu, is there no value to keeping the tests on that qemu target so that we have both? I just want to make sure we aren't losing any meaningful test coverage.

You mean the switch from Cortex-A8 to Cortex-A15? I don't think the matters - they will use the same emulation engine underneath. I only switched because the A15 has some extra features enabled that we needed.

SGTM

[wt]

Other than my comments about cfg expr ordering, LGTM.

Fixed

[jonathanpallant]

rebased