A tiny Open POWER ISA softcore written in VHDL 2008

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Paul Mackerras 7fe84220a5 decode: Avoid multiplexing from instruction reg fields to regfile address ports This aims to simplify the logic between the instruction image and the register file read address ports and reduce the size of the decode tables. With this patch, the input_reg_a column of the decode tables can only select RA or zeroes, the input_reg_b column can only select RB or a constant (0, -1, or an immediate value from the instruction), and the input_reg_c columns can only select RS or zeroes. That means that the rotate/shift/logical ops now have their first input coming in via the input_reg_c column. That means we need to add a read_data3 field to the Decode2ToExecuteType record, but that will go away again when we split out the rotate/mask/logical ops to their own unit. As a related but not tightly connected change, this patch also sets the read1_enable signal to the register file be 0 when RA=0 and the input_reg_a for the instruction is RA_OR_ZERO (previously it was 1). Signed-off-by: Paul Mackerras <paulus@ozlabs.org>		5 years ago
fpga	Improve PLL/MMCM clocks configuration	5 years ago
hello_world	Rebuild hello world assuming a 50MHz clock	5 years ago
scripts	New C based JTAG debug tool	5 years ago
sim-unisim	Add a debug (DMI) bus and a JTAG interface to it on Xilinx FPGAs	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	decode: Push mtspr/mfspr register decoding down into execute1	5 years ago
README.md	Remove gcc software divide patch	5 years ago
common.vhdl	decode: Avoid multiplexing from instruction reg fields to regfile address ports	5 years ago
core.vhdl	Merge branch 'divider' of https://github.com/paulusmack/microwatt	5 years ago
core_debug.vhdl	Add core debug module	5 years ago
core_tb.vhdl	Add core debug module	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	decode: Avoid multiplexing from instruction reg fields to regfile address ports	5 years ago
decode2.vhdl	decode: Avoid multiplexing from instruction reg fields to regfile address ports	5 years ago
decode_types.vhdl	decode: Avoid multiplexing from instruction reg fields to regfile address ports	5 years ago
divider.vhdl	divider: Do absolute-value ops in divider instead of decode	5 years ago
divider_tb.vhdl	divider: Do absolute-value ops in divider instead of decode	5 years ago
dmi_dtm_dummy.vhdl	Fix build issue in dmi_dtm_dummy.vhdl	5 years ago
dmi_dtm_tb.vhdl	Wishbone debug module	5 years ago
dmi_dtm_xilinx.vhdl	Don't reset JTAG request register asynchronously	5 years ago
execute1.vhdl	decode: Avoid multiplexing from instruction reg fields to regfile address ports	5 years ago
execute2.vhdl	Reformat execute2	5 years ago
fetch1.vhdl	Simplify fetch1	5 years ago
fetch2.vhdl	Reformat fetch2	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	Add MCRF instruction	5 years ago
loadstore1.vhdl	Reformat loadstore1	5 years ago
loadstore2.vhdl	loadstore2: Do data formatting after a register stage	5 years ago
microwatt.core	Improve PLL/MMCM clocks configuration	5 years ago
multiply.vhdl	Multiply needs to be 16 stages to fix all timing issues	5 years ago
multiply_tb.vhdl	Reformat multiply_tb	5 years ago
ppc_fx_insns.vhdl	Implement absolute branches	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_jtag.vhdl	Add jtag support in simulation via a socket	5 years ago
sim_jtag_socket.vhdl	Add jtag support in simulation via a socket	5 years ago
sim_jtag_socket_c.c	Add jtag support in simulation via a socket	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	Add core debug module	5 years ago
wishbone_arbiter.vhdl	Use a 3 way WB arbiter and cleanup fpga toplevel	5 years ago
wishbone_debug_master.vhdl	Wishbone debug module	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:

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