Initial QEMU support for Neorv32

[VideoGPU]

Hi, I have started to add QEMU machine model for the NEORV32 .
Currently UART and SPI flash work OK, I was able to run a bootloader + "Hello World" example from an emulated SPI flash file.
The goal is to add more and more features, interrupts, DMA, I2C..
The branch is here:
🔗 https://github.com/VideoGPU/qemu/tree/mlevit_neorv32_riscv_support
And a small readme is here:
🔗 https://github.com/VideoGPU/qemu/blob/mlevit_neorv32_riscv_support/docs/system/riscv/neorv32.rst

[stnolting]

Hey @VideoGPU.

Wow, that's pretty impressive!

I never work with QEMU myself (I'm still a HW person), but I think it could be very helpful for SW developers as a virtual prototype!

Thanks for sharing!

And a small readme is here:
🔗 https://github.com/VideoGPU/qemu/blob/mlevit_neorv32_riscv_support/docs/system/riscv/neorv32.rst

I'll have a closer look at this.

[VideoGPU]

Thanks!
Hope it would be useful, I am mostly in a SW world, and a HW is my hobby.
And I am using NeoRV32 for a few years now, since it is so simple to use, and to add a peripherals!
So this QEMU project, just for faster software workflow.

Michael.

[stnolting]

That's definitely it!

It's been a few years since I worked with QEMU... Do you happen to have a short documentation or example project somewhere to show how to use it to emulate NEORV32?

[VideoGPU]

Yes, actually I am preparing a small git with a more detailed docs and some binaries for testing the QEMU part.
Something like unit tests with expected output - like bootloader's menu or "Hello world" for example.
I believe it would be ready soon, will be glad to post here.

[stnolting]

That's great! Thank you very much! 👍

[VideoGPU]

Hi,
Here is the separate repo for unit-testing and quick start for using NEORV32 binaries on QEMU:
https://github.com/VideoGPU/qemu_neorv32_extras

Currently there are two unit tests - for bootloader and for "Hello World" example stored on emulated flash.
That's it - the full flow of booloader loading the image from SPI flash is tested.

I am curious, what additional features people would like on QEMU simulation?

[stnolting]

Please excuse my late reply...

Here is the separate repo for unit-testing and quick start for using NEORV32 binaries on QEMU:
https://github.com/VideoGPU/qemu_neorv32_extras

That looks really great! Thank you very much for your work!

I am curious, what additional features people would like on QEMU simulation?

Loading the executable is pretty handy. Of course, it would be really cool to have support for the on-chip debugger. Then you could develop software directly on the QEMU version from Eclipse. 😅

[VideoGPU]

Yes, this is the goal ) to test the software on QEMU, and do only the complex work on FPGA - hardware issues, cache sync,etc.
Currently it is possible to debug the Neorv32 firmware with QEMU and gdb, thanks to the great work of Risc-V community.
But it is somehow awkward: I need to run the QEMU from the command line in "wait for gdb" mode.
And after it, open the Eclipse, load the Neorv32 software sources, and connect with gdb. It works pretty well, but a little awkward.
The good thing that I like, is when for example bootloader crashes, it is possible to open the QEMU itself in debug mode as well, and see what is going on "under the hood". Thinking how to simplify the flow.