[arch][riscv][nuclei] Add Nuclei RISC-V processsor support

[fanghuaqi]

Add Nuclei RISC-V Processor Support

• This PR add Nuclei RISC-V Processor which use CLIC interrupt system instead of PLIC and CLINT interrupt system, check Nuclei RISC-V Processor Spec
• This PR is also using Nuclei NMSIS and SDK, see https://github.com/Nuclei-Software/NMSIS and
  https://github.com/Nuclei-Software/nuclei-sdk
• In this PR, the context switch is done using CLIC software interrupt
• For RISC-V CLIC spec, please check https://github.com/riscv/riscv-fast-interrupt/blob/master/clic.adoc
• To evaluate this support, Nuclei HummingBird RISC-V SoC is supported, please check https://nucleisys.com/developboard.php for this board introduction

[fanghuaqi]

How to use this PR

Here are steps used in Linux, similar steps could be done in Windows.

Prerequisites

• Get a Nuclei HummingBird FPGA evaluation board and program an Nuclei RISC-V Core, such as N200/N300/N600 series
• Download Nuclei Studio IDE from https://www.nucleisys.com/download.php

Assume you have extracted Nuclei Studio IDE into ~/NucleiStudio_IDE_202009, then you can open setup toolchain path before build program by command:

export PATH=$HOME/NucleiStudio_IDE_202009/NucleiStudio/toolchain/gcc/bin:$PATH

Build Project for Nuclei HummingBird Evaluation Board

1. cd /path/to/lk

2. make TOOLCHAIN_PREFIX=riscv-nuclei-elf- nuclei-hbird

   linking build-nuclei-hbird/lib/io.mod.o
   generating build-nuclei-hbird/linker-twosegment.ld
   linking build-nuclei-hbird/lk.elf
      text    data     bss     dec     hex filename
       195       0       0     195      c3 ./build-nuclei-hbird/app.mod.o
        34       0       0      34      22 ./build-nuclei-hbird/app/shell.mod.o
     22895      84     188   23167    5a7f ./build-nuclei-hbird/app/tests.mod.o
         0       0       0       0       0 ./build-nuclei-hbird/arch.mod.o
      2938       1    2112    5051    13bb ./build-nuclei-hbird/arch/riscv.mod.o
      1468       0       0    1468     5bc ./build-nuclei-hbird/dev.mod.o
      1992       4      52    2048     800 ./build-nuclei-hbird/external/platform/hbird.mod.o
     13770       0     593   14363    381b ./build-nuclei-hbird/kernel.mod.o
      1989       0      72    2061     80d ./build-nuclei-hbird/kernel/novm.mod.o
      1622       0       0    1622     656 ./build-nuclei-hbird/lib/cbuf.mod.o
      3488      29       9    3526     dc6 ./build-nuclei-hbird/lib/console.mod.o
       860      12       0     872     368 ./build-nuclei-hbird/lib/debug.mod.o
      2778       8       5    2791     ae7 ./build-nuclei-hbird/lib/heap.mod.o
      2272       0      52    2324     914 ./build-nuclei-hbird/lib/heap/miniheap.mod.o
       550      16       4     570     23a ./build-nuclei-hbird/lib/io.mod.o
      8600      16      12    8628    21b4 ./build-nuclei-hbird/lib/libc.mod.o
       233       0       0     233      e9 ./build-nuclei-hbird/platform.mod.o
       417       0     176     593     251 ./build-nuclei-hbird/platform/nuclei-hbird.mod.o
         8       0       0       8       8 ./build-nuclei-hbird/target.mod.o
         6       0       0       6       6 ./build-nuclei-hbird/target/nuclei-hbird.mod.o
      1129       0      16    1145     479 ./build-nuclei-hbird/top.mod.o
     67244     170    3291   70705   11431 (TOTALS)
   generating image: build-nuclei-hbird/lk.bin
      text    data     bss     dec     hex filename
     57568     200    3304   61072    ee90 build-nuclei-hbird/lk.elf
   generating listing: build-nuclei-hbird/lk.elf.lst
   generating listing: build-nuclei-hbird/lk.elf.debug.lst
   generating symbols: build-nuclei-hbird/lk.elf.sym
   generating sorted symbols: build-nuclei-hbird/lk.elf.sym.sorted
   generating size map: build-nuclei-hbird/lk.elf.size
   generating objdump: build-nuclei-hbird/lk.elf.dump
   generating build-nuclei-hbird/srcfiles.txt
   

3. Open Nuclei Studio IDE(~/NucleiStudio_IDE_202009/NucleiStudio/eclipse), and create a Nuclei SDK project for HummingBird SoC by following guidance here in Chinese

4. Open the debug configuration for that project and select executable using the build-nuclei-hbird/lk.elf, and download it and run it, here is the sample output.

   Nuclei SDK Build Time: Oct 28 2020, 11:46:22
   Download Mode: ILM
   CPU Frequency 32000245 Hz
   
   welcome to lk
   
   boot args 0x0 0xa 0x2f 0x2f
   initializing heap
   calling constructors
   initializing mp
   initializing threads
   initializing timers
   initializing ports
   creating bootstrap completion thread
   top of bootstrap2()
   RISCV: Machine mode
   RISCV: mvendorid 0x536 marchid 0x205 mimpid 0x1 mhartid 0x0
   RISCV: misa 0x40101105
   initializing platform
   initializing target
   initializing apps
   starting app shell
   entering main console loop
   ] fibo 4
   fibo 3
   took 3 msecs to calculate
   ] threads
   thread list:
   dump_thread: t 00x90001348 (shell)
          state run, priority 16, remaining quantum -450
          stack 0x900013c8, stack_size 1280, stack_used 464
          entry 0x80000b14, arg 0x8000e044, flags 0x27
          wait queue 0x0, wait queue ret 0
   dump_thread: t 0x90000b04 (idle)
          state rdy, priority 0, remaining quantum 0
          stack 0x0, stack_size 0, stack_used 0
          entry 0x0, arg 0x0, flags 0x11
          wait queue 0x0, wait queue ret 0
          arch: sp 0x0
   ]
   

Thanks
Huaqi

[travisg]

Oh very neat! Very interesting.

The context switch thing we might have to work out a bit, but I'm always interested in new hardware.

[travisg]

Still looking at this one. Trouble is that context switch stuff is far too intrusive. Is it mandatory that the context switch be done via the CLIC? I'd love for this to look much more like the other riscv with the core kernel stuff.

[fanghuaqi]

Yes, it should be done via CLIC, since CLIC introduced, CORE will have exception and interrupt state, if we use current context switch, then we can't get out of interrupt state, which will affect normal interrupt handling.

[travisg]

Closing this in favour of #527, which records what CLIC support in LK would need.

The gap is real — LK's riscv code assumes CLINT plus PLIC and has nothing for the CLIC, so Nuclei cores and anything else using vectored interrupts are unsupported today. Thank you for the thorough write-up and the reproduction steps; they made the re-triage much easier.

Two things keep this from landing as posted. It vendors around 25k lines of NMSIS and the Nuclei SDK, which is more than the tree takes for a single core family now, and the context-switch rework was objected to in review at the time and never resolved. A version that separated the CLIC interrupt-controller support from the vendor headers, and worked out how the CLIC trap path coexists with the existing CLINT/PLIC path instead of replacing it, would have a real path in — that's written up in the issue.