AFOliveira opened a new pull request, #20328:
URL: https://github.com/apache/nuttx/pull/20328
## Summary
Add initial NuttX support for the AIFoundry Erbium Minion core (RV64IMFC).
The chip is in tape-out, so the initial target is the public ET-platform
system emulator, `erbium_emu`. NuttX is loaded as an ELF at `0x40000200`
and runs in machine mode on hart 0; other harts are parked.
### Supported
- Erbium chip support in `arch/risc-v/src/erbium`
- Hart 0 only, SMP disabled, FLAT build
- PLIC interrupt controller (sources 1-6)
- Machine timer (mtime/mtimecmp) as the system timer
- UART0 console, interrupt driven, 8N1
- FPU context switching, using the common RISC-V code
- `minion:nsh` and `minion:ostest` configurations, Make and CMake
- Board documentation, including how to build the emulator
- `tools/test_emu.py` to run prebuilt images in the emulator
### Notes
- Erbium executes `fdiv`/`fsqrt` and `FENCE.I` in microcode, which a
standalone image does not have. The board build files pass `-mno-fdiv`
to GCC when the FPU is enabled, startup initializes the FPU without
`FENCE.I`, and the ELF loader is disabled in both configurations.
- The core has no A extension, so atomics use interrupt masking.
- Reboot is not supported: the emulator's reset register does not reset.
## Impact
- New platform: `arch/risc-v/src/erbium/`, `arch/risc-v/include/erbium/`
and `boards/risc-v/erbium/` are new directories. No existing chip, board,
driver or shared toolchain file is modified.
- `arch/risc-v/Kconfig` and `boards/Kconfig`: new `ARCH_CHIP_ERBIUM` and
`ARCH_BOARD_ERBIUM_MINION` entries added; no existing entries changed.
- `tools/ci/testlist/risc-v-01.dat`: CMake entries for both configurations.
- No nuttx-apps changes.
## Testing
There is no Erbium silicon yet, so all runtime testing is on the emulator.
The series only adds a new chip and board, so it does not change any
existing configuration. I will add hardware logs once silicon is available.
Emulator-only testing has been accepted before, e.g. #8687 (Cortex-R82 on
Arm FVP).
Host: Ubuntu 24.04 x86_64, xPack `riscv-none-elf-gcc` 14.3.0-1 (same as
the CI image), CMake 3.28.3. Emulator: ET-platform
`836a4ab600e93c3059bb58c898edbc37744cd8d0`, unmodified. nuttx-apps
`46e148db093d091fae102c4a4a2294f36dbe24c6` (master), unmodified.
- `tools/testbuild.sh` for `minion:nsh`, `minion:ostest` and
`rv-virt:nsh64`, Make (`-Werror`) and CMake: pass
- `minion:nsh` without FPU: builds and boots
- `ostest`, Make and CMake builds: exit status 0, including the FPU tests
- NSH with four emulator harts running: NuttX stays on hart 0
- No `fdiv`/`fsqrt` or A-extension instructions in any image
- `tools/checkpatch.sh -c -u -m -g`: pass
- `make html` with `-W`: pass
```
$ ./tools/configure.sh -l minion:ostest
$ make -j16
$ erbium_emu -elf_load nuttx -reset_pc 0x40000200 -single_thread \
-max_cycles 100000000000
...
Final memory usage:
VARIABLE BEFORE AFTER
======== ======== ========
arena fc6280 fc6280
ordblks 2 7
mxordblk fc17d0 fbca40
uordblks 47f8 4920
fordblks fc1a88 fc1960
user_main: Exiting
ostest_main: Exiting with status 0
```
```
$ ./tools/configure.sh -l minion:nsh
$ make -j16
$ erbium_emu -elf_load nuttx -reset_pc 0x40000200 -single_thread \
-max_cycles 100000000000
NuttShell (NSH)
nsh> uname -a
NuttX 0.0.0 87efe04801 Sep 23 2026 13:00:47 risc-v minion
nsh> cat /proc/uptime
0.81
nsh> sleep 1
nsh> cat /proc/uptime
2.42
nsh> free
total used free maxused maxfree nused nfree name
16495856 11560 16484296 12640 16483912 24 2 Umem
```
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