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Paul Mackerras
96b402a4bf
All of the PPC add and subtract instructions, including carrying and extended versions, do much the same arithmetic operation: result = (I xor A) + B + C where A is the value from RA, I provides a logical inversion of A (i.e. I is 0 or -1), B is either from RB or is a constant 0 or -1, and C is 0, 1 or the carry bit from XER (CA). To consolidate all the add/subtract instructions into a single OP_ADD, we add a column to decode_rom_t to indicate when A should be inverted, and change the input_carry field to a 3-state selector to select C in the equation above. This also adds a new "CONST_M1" value for input_reg_b_t to indicate that B is a constant -1. This allows us to implement addme and subfme. The addex instruction appears not to exist, so the comments referring to it are removed. Signed-off-by: Paul Mackerras <paulus@ozlabs.org> |
5 years ago | |
|---|---|---|
| fpga | 5 years ago | |
| hello_world | 5 years ago | |
| scripts | 5 years ago | |
| sim-unisim | 5 years ago | |
| tests | 5 years ago | |
| .gitignore | 5 years ago | |
| .travis.yml | 5 years ago | |
| LICENSE | 5 years ago | |
| Makefile | 5 years ago | |
| README.md | 5 years ago | |
| common.vhdl | 5 years ago | |
| core.vhdl | 5 years ago | |
| core_debug.vhdl | 5 years ago | |
| core_tb.vhdl | 5 years ago | |
| cr_file.vhdl | 5 years ago | |
| crhelpers.vhdl | 5 years ago | |
| decode1.vhdl | 5 years ago | |
| decode2.vhdl | 5 years ago | |
| decode_types.vhdl | 5 years ago | |
| divider.vhdl | 5 years ago | |
| divider_tb.vhdl | 5 years ago | |
| dmi_dtm_dummy.vhdl | 5 years ago | |
| dmi_dtm_tb.vhdl | 5 years ago | |
| dmi_dtm_xilinx.vhdl | 5 years ago | |
| execute1.vhdl | 5 years ago | |
| execute2.vhdl | 5 years ago | |
| fetch1.vhdl | 5 years ago | |
| fetch2.vhdl | 5 years ago | |
| glibc_random.vhdl | 5 years ago | |
| glibc_random_helpers.vhdl | 5 years ago | |
| helpers.vhdl | 5 years ago | |
| icache.vhdl | 5 years ago | |
| icache_tb.vhdl | 5 years ago | |
| insn_helpers.vhdl | 5 years ago | |
| loadstore1.vhdl | 5 years ago | |
| loadstore2.vhdl | 5 years ago | |
| microwatt.core | 5 years ago | |
| multiply.vhdl | 5 years ago | |
| multiply_tb.vhdl | 5 years ago | |
| ppc_fx_insns.vhdl | 5 years ago | |
| register_file.vhdl | 5 years ago | |
| sim_console.vhdl | 5 years ago | |
| sim_console_c.c | 5 years ago | |
| sim_jtag.vhdl | 5 years ago | |
| sim_jtag_socket.vhdl | 5 years ago | |
| sim_jtag_socket_c.c | 5 years ago | |
| sim_uart.vhdl | 5 years ago | |
| simple_ram_behavioural.vhdl | 5 years ago | |
| simple_ram_behavioural_helpers.vhdl | 5 years ago | |
| simple_ram_behavioural_helpers_c.c | 5 years ago | |
| simple_ram_behavioural_tb.bin | 5 years ago | |
| simple_ram_behavioural_tb.vhdl | 5 years ago | |
| soc.vhdl | 5 years ago | |
| wishbone_arbiter.vhdl | 5 years ago | |
| wishbone_debug_master.vhdl | 5 years ago | |
| wishbone_types.vhdl | 5 years ago | |
| writeback.vhdl | 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
- 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)