Paul Mackerras
94dd8bc480
For an unaligned load or store, we do the first doubleword (dword) of the transfer as normal, but then go to a new NEXT_DWORD state of the state machine to do the cache tag lookup for the second dword of the transfer. From the NEXT_DWORD state we have much the same transitions to other states as from the IDLE state (the transitions for OP_LOAD_HIT are a bit different but almost identical for the other op values). We now do the preparation of the data to be written in loadstore1, that is, byte reversal if necessary and rotation by a number of bytes based on the low 3 bits of the address. We do rotation not shifting so we have the bytes that need to go into the second doubleword in the right place in the low bytes of the data sent to dcache. The rotation and byte reversal are done in a single step with one multiplexer per byte by setting the select inputs for each byte appropriately. This also fixes writeback to not write the register value until it has received both pieces of an unaligned load value. Signed-off-by: Paul Mackerras <paulus@ozlabs.org> |
5 years ago | |
|---|---|---|
| constraints | 5 years ago | |
| fpga | 5 years ago | |
| hello_world | 5 years ago | |
| media | 5 years ago | |
| micropython | 5 years ago | |
| openocd | 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 | |
| Makefile.synth | 5 years ago | |
| README.md | 5 years ago | |
| cache_ram.vhdl | 5 years ago | |
| common.vhdl | 5 years ago | |
| control.vhdl | 5 years ago | |
| core.vhdl | 5 years ago | |
| core_debug.vhdl | 5 years ago | |
| core_tb.vhdl | 5 years ago | |
| countzero.vhdl | 5 years ago | |
| countzero_tb.vhdl | 5 years ago | |
| cr_file.vhdl | 5 years ago | |
| cr_hazard.vhdl | 5 years ago | |
| crhelpers.vhdl | 5 years ago | |
| dcache.vhdl | 5 years ago | |
| dcache_tb.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 | |
| fetch1.vhdl | 5 years ago | |
| fetch2.vhdl | 5 years ago | |
| glibc_random.vhdl | 5 years ago | |
| glibc_random_helpers.vhdl | 5 years ago | |
| gpr_hazard.vhdl | 5 years ago | |
| helpers.vhdl | 5 years ago | |
| icache.vhdl | 5 years ago | |
| icache_tb.vhdl | 5 years ago | |
| icache_test.bin | 5 years ago | |
| insn_helpers.vhdl | 5 years ago | |
| loadstore1.vhdl | 5 years ago | |
| logical.vhdl | 5 years ago | |
| microwatt.core | 5 years ago | |
| multiply.vhdl | 5 years ago | |
| multiply_tb.vhdl | 5 years ago | |
| plru.vhdl | 5 years ago | |
| plru_tb.vhdl | 5 years ago | |
| ppc_fx_insns.vhdl | 5 years ago | |
| register_file.vhdl | 5 years ago | |
| rotator.vhdl | 5 years ago | |
| rotator_tb.vhdl | 5 years ago | |
| sim_bram.vhdl | 5 years ago | |
| sim_bram_helpers.vhdl | 5 years ago | |
| sim_bram_helpers_c.c | 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 | |
| sim_vhpi_c.c | 5 years ago | |
| sim_vhpi_c.h | 5 years ago | |
| soc.vhdl | 5 years ago | |
| utils.vhdl | 5 years ago | |
| wishbone_arbiter.vhdl | 5 years ago | |
| wishbone_bram_tb.bin | 5 years ago | |
| wishbone_bram_tb.vhdl | 5 years ago | |
| wishbone_bram_wrapper.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
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
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 images. Read through the Makefile for details.
-
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 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=8192 --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)