A tiny Open POWER ISA softcore written in VHDL 2008
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Benjamin Herrenschmidt ee52fd4d80 Add a debug (DMI) bus and a JTAG interface to it on Xilinx FPGAs
This adds a simple bus that can be mastered from an external
system via JTAG, which will be used to hookup various debug
modules.

It's loosely based on the RiscV model (hence the DMI name).

The module currently only supports hooking up to a Xilinx BSCANE2
but it shouldn't be too hard to adapt it to support different TAPs
if necessary.

The JTAG protocol proper is not exactly the RiscV one at this point,
though I might still change it.

This comes with some sim variants of Xilinx BSCANE2 and BUFG and a
test bench.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
fpga
hello_world
scripts Add a debug (DMI) bus and a JTAG interface to it on Xilinx FPGAs 5 years ago
sim-unisim Add a debug (DMI) bus and a JTAG interface to it on Xilinx FPGAs 5 years ago
tests
.gitignore
.travis.yml
LICENSE
Makefile Add a debug (DMI) bus and a JTAG interface to it on Xilinx FPGAs 5 years ago
README.md
common.vhdl
core.vhdl
core_tb.vhdl
cr_file.vhdl
crhelpers.vhdl Reformat crhelpers, and remove some stale code 5 years ago
decode1.vhdl
decode2.vhdl
decode_types.vhdl
dmi_dtm_dummy.vhdl Add a debug (DMI) bus and a JTAG interface to it on Xilinx FPGAs 5 years ago
dmi_dtm_tb.vhdl Add a debug (DMI) bus and a JTAG interface to it on Xilinx FPGAs 5 years ago
dmi_dtm_xilinx.vhdl Add a debug (DMI) bus and a JTAG interface to it on Xilinx FPGAs 5 years ago
execute1.vhdl
execute2.vhdl
fetch1.vhdl
fetch2.vhdl
glibc_random.vhdl
glibc_random_helpers.vhdl
helpers.vhdl Reformat helpers 5 years ago
icache.vhdl
icache_tb.vhdl
insn_helpers.vhdl Reformat insn_helpers 5 years ago
loadstore1.vhdl
loadstore2.vhdl
microwatt.core Add a debug (DMI) bus and a JTAG interface to it on Xilinx FPGAs 5 years ago
multiply.vhdl
multiply_tb.vhdl
ppc_fx_insns.vhdl
register_file.vhdl
sim_console.vhdl
sim_console_c.c
sim_uart.vhdl
simple_ram_behavioural.vhdl
simple_ram_behavioural_helpers.vhdl
simple_ram_behavioural_helpers_c.c
simple_ram_behavioural_tb.bin
simple_ram_behavioural_tb.vhdl
soc.vhdl Add a debug (DMI) bus and a JTAG interface to it on Xilinx FPGAs 5 years ago
wishbone_arbiter.vhdl Use a 3 way WB arbiter and cleanup fpga toplevel 5 years ago
wishbone_types.vhdl
writeback.vhdl

README.md

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

  • 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
git clone https://github.com/mikey/micropython
cd micropython
git checkout powerpc
cd ports/powerpc
make -j$(nproc)
cd ../../../
  • Microwatt uses ghdl for simulation. Either install this from your distro or build it. Next build microwatt:
git clone https://github.com/antonblanchard/microwatt
cd microwatt
make
  • Link in the micropython image:
ln -s ../micropython/ports/powerpc/build/firmware.bin simple_ram_behavioural.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
  • 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):
fusesoc run --target=nexys_video microwatt --memory_size=8192 --ram_init_file=/path/to/microwatt/fpga/hello_world.hex
  • 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:

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