arch:riscv64:basic porting for C906.

[hotislandn]

Summary

This patch enables Nuttx basic OS functionalities on C906, a RISC-V 64bit SoC that implements RV64GCVX extensions from T-HEAD.

Impact

RV64GC targets.

Testing

1. need to build with the toolchain from T-HEAD website, which enables the specific extentisons
2. 'ostest' runs on C906 within QEMU(cskysim)

[acassis]

Hi @hotislandn thank you very much for adding support on NuttX for Allwinner C906 !

I think you missed to run nxstyle/checkpatch on some files:

Warning: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/arch/risc-v/include/c906/chip.h:24:1: warning: #include outside of 'Included Files' section
Warning: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/arch/risc-v/include/c906/chip.h:25:1: warning: #include outside of 'Included Files' section
Warning: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/arch/risc-v/include/c906/chip.h:26:1: warning: #include outside of 'Included Files' section
Warning: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/arch/risc-v/include/c906/chip.h:28:1: warning: #include outside of 'Included Files' section
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/arch/risc-v/src/c906/c906_idle.c:2:1: error: Too many whitespaces before relative file path
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/arch/risc-v/src/c906/c906_lowputc.c:85:63: error: Left bracket not on separate line
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/arch/risc-v/src/c906/c906_lowputc.c:85:4: error: Bad alignment
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/arch/risc-v/src/c906/c906_lowputc.h:33:3: error: Invalid section for this file type
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/arch/risc-v/src/c906/c906_serial.c:263:83: error: Long line found
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/arch/risc-v/src/c906/c906_serial.c:310:79: error: Long line found
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/arch/risc-v/src/c906/c906_start.c:81:6: error: Missing whitespace after keyword
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/boards/risc-v/c906/smartl-c906/include/board.h:2:1: error: Relative file path does not match actual file
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/boards/risc-v/c906/smartl-c906/src/c906_leds.c:31:1: error: Too many blank lines
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/boards/risc-v/c906/smartl-c906/src/c906_leds.c:38:1: error: Blank line follows left brace
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/boards/risc-v/c906/smartl-c906/src/c906_leds.c:39:1: error: Blank line precedes right brace at line
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/boards/risc-v/c906/smartl-c906/src/c906_leds.c:43:1: error: Blank line follows left brace
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/boards/risc-v/c906/smartl-c906/src/c906_leds.c:44:1: error: Blank line precedes right brace at line
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/boards/risc-v/c906/smartl-c906/src/c906_leds.c:48:1: error: Blank line follows left brace
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/boards/risc-v/c906/smartl-c906/src/c906_leds.c:49:1: error: Blank line precedes right brace at line
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/boards/risc-v/c906/smartl-c906/src/smartl-c906.h:2:1: error: Relative file path does not match actual file
Error: Process completed with exit code 1.

[hotislandn]

Hi @hotislandn thank you very much for adding support on NuttX for Allwinner C906 !

I think you missed to run nxstyle/checkpatch on some files:

Warning: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/arch/risc-v/include/c906/chip.h:24:1: warning: #include outside of 'Included Files' section
Warning: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/arch/risc-v/include/c906/chip.h:25:1: warning: #include outside of 'Included Files' section
Warning: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/arch/risc-v/include/c906/chip.h:26:1: warning: #include outside of 'Included Files' section
Warning: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/arch/risc-v/include/c906/chip.h:28:1: warning: #include outside of 'Included Files' section
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/arch/risc-v/src/c906/c906_idle.c:2:1: error: Too many whitespaces before relative file path
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/arch/risc-v/src/c906/c906_lowputc.c:85:63: error: Left bracket not on separate line
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/arch/risc-v/src/c906/c906_lowputc.c:85:4: error: Bad alignment
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/arch/risc-v/src/c906/c906_lowputc.h:33:3: error: Invalid section for this file type
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/arch/risc-v/src/c906/c906_serial.c:263:83: error: Long line found
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/arch/risc-v/src/c906/c906_serial.c:310:79: error: Long line found
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/arch/risc-v/src/c906/c906_start.c:81:6: error: Missing whitespace after keyword
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/boards/risc-v/c906/smartl-c906/include/board.h:2:1: error: Relative file path does not match actual file
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/boards/risc-v/c906/smartl-c906/src/c906_leds.c:31:1: error: Too many blank lines
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/boards/risc-v/c906/smartl-c906/src/c906_leds.c:38:1: error: Blank line follows left brace
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/boards/risc-v/c906/smartl-c906/src/c906_leds.c:39:1: error: Blank line precedes right brace at line
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/boards/risc-v/c906/smartl-c906/src/c906_leds.c:43:1: error: Blank line follows left brace
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/boards/risc-v/c906/smartl-c906/src/c906_leds.c:44:1: error: Blank line precedes right brace at line
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/boards/risc-v/c906/smartl-c906/src/c906_leds.c:48:1: error: Blank line follows left brace
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/boards/risc-v/c906/smartl-c906/src/c906_leds.c:49:1: error: Blank line precedes right brace at line
Error: /home/runner/work/incubator-nuttx/incubator-nuttx/nuttx/boards/risc-v/c906/smartl-c906/src/smartl-c906.h:2:1: error: Relative file path does not match actual file
Error: Process completed with exit code 1.

Hi Acassis,

Yes, I failed to do this which lead to those style check failures. I will update them soon.
BTW, for another 2 build errors, which caused by the wrong toolchain used for C906, it needs a specific toolchain from T-HEAD.
How to add this dedicated toolchain for the C906 build, or we have to use the standard toolchain but lose any vendor ISA extensions?
Thanks a lot!

[Ouss4]

How to add this dedicated toolchain for the C906 build, or we have to use the standard toolchain but lose any vendor ISA extensions?

You can check arch/risc-v/src/rv32im&rv64gc/Toolchain.defs for how to add a toolchain. For our CI to be able to build, the toolchain needs to be installed in the Docker image as well (https://github.com/apache/incubator-nuttx-testing/blob/master/docker/linux/Dockerfile)
That said a quick (and maybe dirty) solution right now is to just disable C906 builds (see https://github.com/apache/incubator-nuttx-testing/blob/master/testlist/other.dat#L4-L6). Configs beginning with a - are ignored.

[Ouss4]

or we have to use the standard toolchain but lose any vendor ISA extensions?

BTW, you can make the default configuration use the SiFive toolchain that's used by the rest of the RISC-V chips and add a config that uses the vendor's toolchain. In this case simple examples can be built without the need of another toolchain.

[btashton]

I'm a little hesitant to bring in the overhead of the ISA vector extensions that are pre 1.0 (Linux does not support them for this reason). Are there other ISA extensions that are causing issues. To be clear I am not saying no, I just want to make sure we are not signing up for what will be legacy baggage from the start.

When I designed that docker image I did it with the idea in mind that we might want to have multiple targets to keep the size from getting crazy. macOS we probably do not want to burden with a lot of special toolchains, but we already have some fairly reasonable coverage there.

[hotislandn]

or we have to use the standard toolchain but lose any vendor ISA extensions?

BTW, you can make the default configuration use the SiFive toolchain that's used by the rest of the RISC-V chips and add a config that uses the vendor's toolchain. In this case simple examples can be built without the need of another toolchain.

Yes, I would like to try this option first, to align with the standard toolchain from SiFive, though we may suffer a bit of performance loss at the beginning. However, this gives better compatibility.
Thanks!

[hotislandn]

I'm a little hesitant to bring in the overhead of the ISA vector extensions that are pre 1.0 (Linux does not support them for this reason). Are there other ISA extensions that are causing issues. To be clear I am not saying no, I just want to make sure we are not signing up for what will be legacy baggage from the start.

When I designed that docker image I did it with the idea in mind that we might want to have multiple targets to keep the size from getting crazy. macOS we probably do not want to burden with a lot of special toolchains, but we already have some fairly reasonable coverage there.

The reason for C906 has to use the vendor-specific toolchain is that T-HEAD adds their own instructions to the "I" extension, not the "V" variant. And, in fact, the "V" spec supported by C906 is 0.7.1.
I guess we are not going to bring the "V" extension into NuttX at this stage. Anyway, I will try to keep it in accordance with the standard toolchain for this patch.
Have a nice day!

[btashton]

A couple minor comments on some copyright headers but looks good to me otherwise as a great starting point