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bbae2d1eda
This changes decode_op_31_array from being indexed by a ppc_insn_t (which is derived from the instruction word by a whole series of if/elsif statements) to being indexed directly by bits 10...1 of the instruction word. With this we no longer need ppc_insn. This then means that the decode1 stage doesn't distinguish between mfcr and mfocrf, or between mtcrf and mtocrf, since those are distinguished by the value in bit 20 of the instruction. To accommodate that, execute1 changes so that the one op value (OP_MFCR) does either the mfcr or the mfocrf behaviour depending on bit 20 of the instruction word; and similarly for mtcrf/mtocrf. Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
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)