allwinner/nezha: new risc-v platform

[paralin]

Adds support for the RISC-V Allwinner Nezha.

[paralin]

Works up to a certain point in u-boot process:

Scanning mmc 0:1...
Found /boot/extlinux/extlinux.conf
Retrieving file: /boot/extlinux/extlinux.conf
1:      SkiffOS
Retrieving file: /rootfs.cpio.lz4
Retrieving file: /Image
append: console=ttyS0,115200 root=/dev/ram0 rw init=/lib/systemd/systemd
Retrieving file: /sun20i-d1-nezha.dtb
Moving Image from 0x40040000 to 0x40200000, end=417dfbc8
## Flattened Device Tree blob at 41800000
   Booting using the fdt blob at 0x41800000
ERROR: Failed to allocate 0x7688268 bytes below 0x42e00000.
ramdisk - allocation error

... most likely the initramfs is too large (for the 1GB memory).

Will test a few things to confirm this is the reason.

[paralin]

Needs further boot debugging. But mostly there.

[paralin]

Status: boots to kernel, everything else not tested yet.

Next focus is to get the newer kernel running.

Known issues:

• newer kernel does not work: using older one (5.14.x)
• u-boot has to run twice for it to work
  • most likely related to watchdog at 18 seconds
  • possible solutions:
    • u-boot: service watchdog while loading images
    • wait to enable watchdog until images are loaded
  • disable watchdog entirely for now? (WDT)
• u-boot: must change the loading addresses:
  • the kernel for skiffos is too large for defaults
  • the defaults in u-boot expect a ~8MB kernel max.
  • fix: copy arm64 settings to riscv section at configs/sunxi-common.h:207
  • fix: or enable the arm64 blocks instead of the risc-v blocks
• need to re-enable KASR and compression when possible

[paralin]

[paralin]

The system now boots & is ssh-accessible, albeit with some features disabled:

[paralin]

[paralin]

Networking + internet works :)

[paralin]

Now everything works. Testing with all optimizations & security opts enabled now.

[paralin]