microwatt

A tiny Open POWER ISA softcore written in VHDL 2008

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Paul Mackerras b3799c432b decode1: Add a stash buffer to the output This means that the busy signal from execute1 (which can be driven combinatorially from mmu or dcache) now stops at decode1 and doesn't go on to icache or fetch1. This helps with timing. Signed-off-by: Paul Mackerras <paulus@ozlabs.org>		5 years ago
.github/workflows	Move from travis to github workflow	5 years ago
constraints	…
fpga	uart: Remove combinational loops on ack and stall signal	5 years ago
hello_world	…
include	spi: Add booting from flash to litedram init	5 years ago
lib	sw: Properly mask syscon register fields	5 years ago
litedram	spi: Add booting from flash to litedram init	5 years ago
media	…
micropython	…
openocd	flash-arty: update error message (#203 )	5 years ago
rust_lib_demo	…
scripts	Add core logging	5 years ago
sim-unisim	…
tests	tests/xics: Fix assumption that interrupts happen immediately	5 years ago
verilator	Pass clock frequency to UART sim wrapper	5 years ago
.gitignore	gitignore: Add more exlusions	5 years ago
LICENSE	…
Makefile	core: Remove fetch2 pipeline stage	5 years ago
README.md	Add Makefile command line variables to enable docker and podman	5 years ago
cache_ram.vhdl	dcache: Rework RAM wrapper to synthetize better on Xilinx	5 years ago
common.vhdl	core: Use a busy signal rather than a stall	5 years ago
control.vhdl	core: Use a busy signal rather than a stall	5 years ago
core.vhdl	decode1: Add a stash buffer to the output	5 years ago
core_debug.vhdl	Add core logging	5 years ago
core_dram_tb.vhdl	spi: Add simulation support	5 years ago
core_flash_tb.vhdl	spi: Add simulation support	5 years ago
core_tb.vhdl	spi: Add SPI Flash controller	5 years ago
countzero.vhdl	…
countzero_tb.vhdl	Exit cleanly from testbench on success	5 years ago
cr_file.vhdl	Add core logging	5 years ago
cr_hazard.vhdl	core: Use a busy signal rather than a stall	5 years ago
crhelpers.vhdl	…
dcache.vhdl	dcache: Reduce back-to-back store latency from 3 cycles to 2	5 years ago
dcache_tb.vhdl	Exit cleanly from testbench on success	5 years ago
decode1.vhdl	decode1: Add a stash buffer to the output	5 years ago
decode2.vhdl	decode: Work out ispr1/ispr2 in parallel with decode ROM lookup	5 years ago
decode_types.vhdl	core: Do addpcis using the main adder (#189 )	5 years ago
divider.vhdl	…
divider_tb.vhdl	Exit cleanly from testbench on success	5 years ago
dmi_dtm_dummy.vhdl	…
dmi_dtm_tb.vhdl	…
dmi_dtm_xilinx.vhdl	dmi: Add ASYNC_REG attribute on synchronizers (#200 )	5 years ago
dram_tb.vhdl	litedram: Improve dram_tb error output	5 years ago
execute1.vhdl	loadstore1: Reduce busy cycles	5 years ago
fetch1.vhdl	icache: Improve latencies when reloading cache lines	5 years ago
glibc_random.vhdl	…
glibc_random_helpers.vhdl	…
gpr_hazard.vhdl	core: Use a busy signal rather than a stall	5 years ago
helpers.vhdl	…
icache.vhdl	icache: Improve latencies when reloading cache lines	5 years ago
icache_tb.vhdl	core: Remove fetch2 pipeline stage	5 years ago
icache_test.bin	…
insn_helpers.vhdl	Implement the addpcis instruction	5 years ago
loadstore1.vhdl	loadstore1: Reduce busy cycles	5 years ago
logical.vhdl	…
microwatt.core	multiply: Use DSP48 slices for multiplication on Xilinx FPGAs	5 years ago
mmu.vhdl	mmu: Take an extra cycle to do TLB invalidations	5 years ago
multiply.vhdl	multiply: Move selection of result bits into execute1	5 years ago
multiply_tb.vhdl	multiply: Move selection of result bits into execute1	5 years ago
plru.vhdl	…
plru_tb.vhdl	Exit cleanly from testbench on success	5 years ago
ppc_fx_insns.vhdl	…
register_file.vhdl	Add core logging	5 years ago
rotator.vhdl	…
rotator_tb.vhdl	Exit cleanly from testbench on success	5 years ago
sim_bram.vhdl	…
sim_bram_helpers.vhdl	…
sim_bram_helpers_c.c	…
sim_console.vhdl	…
sim_console_c.c	…
sim_jtag.vhdl	…
sim_jtag_socket.vhdl	…
sim_jtag_socket_c.c	…
sim_no_flash.vhdl	spi: Add simulation support	5 years ago
sim_uart.vhdl	…
sim_vhpi_c.c	…
sim_vhpi_c.h	…
soc.vhdl	bram: Remove combinational loop on stall	5 years ago
spi_flash_ctrl.vhdl	spi: Add SPI Flash controller	5 years ago
spi_rxtx.vhdl	spi: Add SPI Flash controller	5 years ago
sync_fifo.vhdl	litedram: Add an L2 cache with store queue	5 years ago
syscon.vhdl	syscon: Remove combinational loop on ack and stall	5 years ago
utils.vhdl	litedram: Add support for booting without BRAM	5 years ago
wishbone_arbiter.vhdl	…
wishbone_bram_tb.bin	…
wishbone_bram_tb.vhdl	Exit cleanly from testbench on success	5 years ago
wishbone_bram_wrapper.vhdl	…
wishbone_debug_master.vhdl	…
wishbone_types.vhdl	soc: Rework interconnect	5 years ago
writeback.vhdl	core: Use a busy signal rather than a stall	5 years ago
xics.vhdl	irq: Simplify xics->core irq input	5 years ago
xilinx-mult.vhdl	multiply: Use DSP48 slices for multiplication on Xilinx FPGAs	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)