A tiny Open POWER ISA softcore written in VHDL 2008
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Michael Neuling f9654428ff
Merge pull request #296 from LarsAsplund/logging-checking
Replaced VHDL assert and report with VUnit checking and logging
3 years ago
.github/workflows Run VUnit tests in CI 3 years ago
constraints Initial support for ghdl synthesis 5 years ago
fpga Merge pull request #277 from paulus/gpio 4 years ago
hello_world Reduce hello_world footprint to fit in 8kB 4 years ago
include arty_a7: Add litesdcard interface 4 years ago
lib console: Add support for the 16550 UART 4 years ago
litedram fpga: Add support for Genesys2 4 years ago
liteeth liteeth: Hook up LiteX LiteEth ethernet controller 4 years ago
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micropython tests: Add updated micropython build with 16550 support 4 years ago
openocd openocd: Fix verify command for v0.10 4 years ago
rust_lib_demo console: Cleanup console API 4 years ago
scripts decode: Add a facility field to the instruction decode tables 4 years ago
sim-unisim Add a debug (DMI) bus and a JTAG interface to it on Xilinx FPGAs 5 years ago
tests MMU: Implement a vestigial partition table 3 years ago
uart16550 Add uart16550 files from fusesoc 4 years ago
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.gitignore Add yosys builds files to gitignore 4 years ago
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core.vhdl icache: Snoop writes to memory by other agents 4 years ago
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decode1.vhdl MMU: Implement a vestigial partition table 3 years ago
decode2.vhdl core: Allow multiple loadstore instructions to be in flight 4 years ago
decode_types.vhdl core: Crack update-form loads into two internal ops 4 years ago
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fetch1.vhdl core: Move redirect and interrupt delivery logic to writeback 4 years ago
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gpio.vhdl Add a GPIO controller and use it to drive the shield I/O pins on the Arty 4 years ago
helpers.vhdl core: Add support for single-precision FP loads and stores 4 years ago
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logical.vhdl core: Make result multiplexing explicit 4 years ago
microwatt.core Merge pull request #277 from paulus/gpio 4 years ago
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ppc_fx_insns.vhdl core: Implement the cmpeqb and cmprb instructions 4 years ago
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README.md

Microwatt

Microwatt

A tiny Open POWER ISA softcore written in VHDL 2008. It aims to be simple and easy to understand.

Simulation using ghdl

MicroPython running on Microwatt

You can try out Microwatt/Micropython without hardware by using the ghdl simulator. If you want to build directly for a hardware target board, see below.

  • Build micropython. If you aren't building on a ppc64le box you will need a cross compiler. If it isn't available on your distro grab the powerpc64le-power8 toolchain from https://toolchains.bootlin.com. You may need to set the CROSS_COMPILE environment variable to the prefix used for your cross compilers. The default is powerpc64le-linux-gnu-.
git clone https://github.com/micropython/micropython.git
cd micropython
cd ports/powerpc
make -j$(nproc)
cd ../../../

A prebuilt micropython image is also available in the micropython/ directory.

  • Microwatt uses ghdl for simulation. Either install this from your distro or build it. Microwatt requires ghdl to be built with the LLVM or gcc backend, which not all distros do (Fedora does, Debian/Ubuntu appears not to). ghdl with the LLVM backend is likely easier to build.

    If building ghdl from scratch is too much for you, the microwatt Makefile supports using Docker or Podman.

  • Next build microwatt:

git clone https://github.com/antonblanchard/microwatt
cd microwatt
make

To build using Docker:

make DOCKER=1

and to build using Podman:

make PODMAN=1
  • Link in the micropython image:
ln -s ../micropython/ports/powerpc/build/firmware.bin main_ram.bin

Or if you were using the pre-built image:

ln -s micropython/firmware.bin main_ram.bin
  • Now run microwatt, sending debug output to /dev/null:
./core_tb > /dev/null

Synthesis on Xilinx FPGAs using Vivado

  • Install Vivado (I'm using the free 2019.1 webpack edition).

  • Setup Vivado paths:

source /opt/Xilinx/Vivado/2019.1/settings64.sh
  • Install FuseSoC:
pip3 install --user -U fusesoc

Fedora users can get FuseSoC package via

sudo dnf copr enable sharkcz/danny
sudo dnf install fusesoc
  • If this is your first time using fusesoc, initialize fusesoc. This is needed to be able to pull down fussoc library components referenced by microwatt. Run
fusesoc init
  • Create a working directory and point FuseSoC at microwatt:
mkdir microwatt-fusesoc
cd microwatt-fusesoc
fusesoc library add microwatt /path/to/microwatt/
  • Build using FuseSoC. For hello world (Replace nexys_video with your FPGA board such as --target=arty_a7-100): You may wish to ensure you have installed Digilent Board files or appropriate files for your board first.
fusesoc run --target=nexys_video microwatt --memory_size=16384 --ram_init_file=/path/to/microwatt/fpga/hello_world.hex

You should then be able to see output via the serial port of the board (/dev/ttyUSB1, 115200 for example assuming standard clock speeds). There is a know bug where initial output may not be sent - try the reset (not programming button) on your board if you don't see anything.

  • To build micropython (currently requires 1MB of BRAM eg an Artix-7 A200):
fusesoc run --target=nexys_video microwatt

Testing

  • A simple test suite containing random execution test cases and a couple of micropython test cases can be run with:
make -j$(nproc) check

Issues

This is functional, but very simple. We still have quite a lot to do:

  • There are a few instructions still to be implemented
  • Need to add caches and bypassing (in progress)
  • Need to add supervisor state (in progress)