microwatt

A tiny Open POWER ISA softcore written in VHDL 2008

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Paul Mackerras 41d28bbdfc Merge pull request #198 from ozbenh/litedram Litedram: Timing improvements		5 years ago
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control.vhdl	core: Improve core reset	5 years ago
core.vhdl	icache: Fix icbi potentially clobbering the icache (#192 )	5 years ago
core_debug.vhdl	debug: Provide a way to examine GPRs, fast SPRs and MSR	5 years ago
core_dram_tb.vhdl	litedram: Remove remnants of riscv-inits	5 years ago
core_tb.vhdl	soc: Rework interconnect	5 years ago
countzero.vhdl	countzero: Add a register to help make timing	5 years ago
countzero_tb.vhdl	Exit cleanly from testbench on success	5 years ago
cr_file.vhdl	Dump CTR, LR and CR on sim termination, and update our tests	5 years ago
cr_hazard.vhdl	sprs: Store common SPRs in register file	5 years ago
crhelpers.vhdl	crhelpers: Constraint "crnum" integer	5 years ago
dcache.vhdl	dcache: Rework RAM wrapper to synthetize better on Xilinx	5 years ago
dcache_tb.vhdl	Exit cleanly from testbench on success	5 years ago
decode1.vhdl	decode1: Reformat to 4-space indentation	5 years ago
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decode_types.vhdl	core: Do addpcis using the main adder (#189 )	5 years ago
divider.vhdl	execute1: Remember dest GPR, RC, OE, XER for slow operations	5 years ago
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dmi_dtm_dummy.vhdl	Fix build issue in dmi_dtm_dummy.vhdl	5 years ago
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insn_helpers.vhdl	Implement the addpcis instruction	5 years ago
loadstore1.vhdl	MMU: Implement reading of the process table	5 years ago
logical.vhdl	execute: Move popcnt and prty instructions into the logical unit	5 years ago
microwatt.core	litedram: Add an L2 cache with store queue	5 years ago
mmu.vhdl	MMU: Implement reading of the process table	5 years ago
multiply.vhdl	execute1: Remember dest GPR, RC, OE, XER for slow operations	5 years ago
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plru.vhdl	plru: Improve sensitivity list	5 years ago
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ppc_fx_insns.vhdl	sprs: Store common SPRs in register file	5 years ago
register_file.vhdl	debug: Provide a way to examine GPRs, fast SPRs and MSR	5 years ago
rotator.vhdl	Implement the extswsli instruction	5 years ago
rotator_tb.vhdl	Exit cleanly from testbench on success	5 years ago
sim_bram.vhdl	ram: Rework main RAM interface	5 years ago
sim_bram_helpers.vhdl	ram: Rework main RAM interface	5 years ago
sim_bram_helpers_c.c	Consolidate VHPI code	5 years ago
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sim_jtag.vhdl	Add jtag support in simulation via a socket	5 years ago
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sim_uart.vhdl	Wire up sim uart TX interrupt	5 years ago
sim_vhpi_c.c	Consolidate VHPI code	5 years ago
sim_vhpi_c.h	Consolidate VHPI code	5 years ago
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wishbone_arbiter.vhdl	wb_arbiter: Early master selection	5 years ago
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wishbone_debug_master.vhdl	wishbone_debug_master: Fix address auto-increment for memory writes	5 years ago
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writeback.vhdl	execute1: Simplify the interrupt logic a little	5 years ago
xics.vhdl	irq: Simplify xics->core irq input	5 years ago

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

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

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):

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)