A tiny Open POWER ISA softcore written in VHDL 2008

openpower ppc64le processor vhdl

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Paul Mackerras d5bc6c8824 Add a divider unit and a testbench for it This adds a divider unit, connected to the core in much the same way that the multiplier unit is connected. The division algorithm is very simple-minded, taking 64 clock cycles for any division (even 32-bit division instructions). The decoding is simplified by making use of regularities in the instruction encoding for div* and mod* instructions. Instead of having PPC_* encodings from the first-stage decoder for each of the different div* and mod* instructions, we now just have PPC_DIV and PPC_MOD, and the inputs to the divider that indicate what sort of division operation to do are derived from instruction word bits. Signed-off-by: Paul Mackerras <paulus@ozlabs.org>		5 years ago
fpga	SOC memory wishbone should clear ACK regardless of STB	5 years ago
hello_world	Rebuild hello world assuming a 50MHz clock	5 years ago
scripts	Fix verific script with new VHDL files	5 years ago
tests	Initial import of microwatt	5 years ago
.gitignore	Add new files to git ignore	5 years ago
.travis.yml	Allow a full make check on Travis	5 years ago
LICENSE	Initial import of microwatt	5 years ago
Makefile	Add a divider unit and a testbench for it	5 years ago
README.md	Add pretty gif demo of MicroPython on Microwatt to README.md	5 years ago
common.vhdl	Add a divider unit and a testbench for it	5 years ago
core.vhdl	Add a divider unit and a testbench for it	5 years ago
core_tb.vhdl	Add a simple direct mapped icache	5 years ago
cr_file.vhdl	Reformat CR file	5 years ago
crhelpers.vhdl	Reformat crhelpers, and remove some stale code	5 years ago
decode1.vhdl	Add a divider unit and a testbench for it	5 years ago
decode2.vhdl	Add a divider unit and a testbench for it	5 years ago
decode_types.vhdl	Add a divider unit and a testbench for it	5 years ago
divider.vhdl	Add a divider unit and a testbench for it	5 years ago
divider_tb.vhdl	Add a divider unit and a testbench for it	5 years ago
execute1.vhdl	Add a divider unit and a testbench for it	5 years ago
execute2.vhdl	Reformat execute2	5 years ago
fetch1.vhdl	Add a default value for RESET_ADDRESS	5 years ago
fetch2.vhdl	Add a simple direct mapped icache	5 years ago
glibc_random.vhdl	Reformat glibc_random	5 years ago
glibc_random_helpers.vhdl	Reformat glibc_random	5 years ago
helpers.vhdl	Reformat helpers	5 years ago
icache.vhdl	Add a simple direct mapped icache	5 years ago
icache_tb.vhdl	Add an icache testbench	5 years ago
insn_helpers.vhdl	Reformat insn_helpers	5 years ago
loadstore1.vhdl	Reformat loadstore1	5 years ago
loadstore2.vhdl	Reformat loadstore2	5 years ago
microwatt.core	Add a divider unit and a testbench for it	5 years ago
multiply.vhdl	Reformat multiply code	5 years ago
multiply_tb.vhdl	Reformat multiply_tb	5 years ago
ppc_fx_insns.vhdl	Remove dynamic ranges from code	5 years ago
register_file.vhdl	Reformat register file	5 years ago
sim_console.vhdl	Reformat sim_console	5 years ago
sim_console_c.c	Make sim poll non-blocking	5 years ago
sim_uart.vhdl	Share soc.vhdl between FPGA and sim	5 years ago
simple_ram_behavioural.vhdl	Reformat simple_ram_behavioural	5 years ago
simple_ram_behavioural_helpers.vhdl	Reformat simple_ram_behavioural	5 years ago
simple_ram_behavioural_helpers_c.c	Silence some loadstore related debug	5 years ago
simple_ram_behavioural_tb.bin	Initial import of microwatt	5 years ago
simple_ram_behavioural_tb.vhdl	Reformat simple_ram_behavioural	5 years ago
soc.vhdl	Switch soc to use std_ulogic	5 years ago
wishbone_arbiter.vhdl	Reformat wishbone code	5 years ago
wishbone_types.vhdl	Reformat wishbone code	5 years ago
writeback.vhdl	Add a divider unit and a testbench for it	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

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)