A tiny Open POWER ISA softcore written in VHDL 2008
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Benjamin Herrenschmidt b863791e38
icache: Fix icbi potentially clobbering the icache (#192)
icbi currently just resets the icache. This has some nasty side
effects such as also clearing the TLB, but also the wishbone interface.

That means that any ongoing cycle will be dropped.

However, most of our slaves don't handle that well and will continue
sending acks for already issued requests.

Under some circumstances we can thus restart an icache load and get
spurious ack/data from the wishbone left over from the "cancelled"
sequence.

This has broken booting Linux for me.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
constraints Initial support for ghdl synthesis 5 years ago
fpga litedram: Add support for booting without BRAM 5 years ago
hello_world Makefile: Improve clean a bit 5 years ago
include litedram: Add support for booting without BRAM 5 years ago
lib litedram: Update to new LiteX/LiteDRAM version 5 years ago
litedram litedram: Make the L2 twice as tall 5 years ago
media Add title image 5 years ago
micropython Update micropython 5 years ago
openocd flash-arty: Add support for specifying the file type 5 years ago
rust_lib_demo console: Move console files 5 years ago
scripts bin2hex: Make sure to generate little endian files 5 years ago
sim-unisim Add a debug (DMI) bus and a JTAG interface to it on Xilinx FPGAs 5 years ago
tests Merge pull request #183 from shawnanastasio/addpcis 5 years ago
verilator Pass clock frequency to UART sim wrapper 5 years ago
.gitignore Add VHDL TAGS 5 years ago
.travis.yml Allow a full make check on Travis 5 years ago
LICENSE
Makefile litedram: Remove old "VexRiscV" based initializations 5 years ago
README.md Add Makefile command line variables to enable docker and podman 5 years ago
cache_ram.vhdl dcache: Rework RAM wrapper to synthetize better on Xilinx 5 years ago
common.vhdl irq: Simplify xics->core irq input 5 years ago
control.vhdl core: Improve core reset 5 years ago
core.vhdl icache: Fix icbi potentially clobbering the icache (#192) 5 years ago
core_debug.vhdl debug: Provide a way to examine GPRs, fast SPRs and MSR 5 years ago
core_dram_tb.vhdl litedram: Add support for booting without BRAM 5 years ago
core_tb.vhdl soc: Rework interconnect 5 years ago
countzero.vhdl countzero: Add a register to help make timing 5 years ago
countzero_tb.vhdl Exit cleanly from testbench on success 5 years ago
cr_file.vhdl Dump CTR, LR and CR on sim termination, and update our tests 5 years ago
cr_hazard.vhdl sprs: Store common SPRs in register file 5 years ago
crhelpers.vhdl crhelpers: Constraint "crnum" integer 5 years ago
dcache.vhdl dcache: Rework RAM wrapper to synthetize better on Xilinx 5 years ago
dcache_tb.vhdl Exit cleanly from testbench on success 5 years ago
decode1.vhdl core: Do addpcis using the main adder (#189) 5 years ago
decode2.vhdl core: Do addpcis using the main adder (#189) 5 years ago
decode_types.vhdl core: Do addpcis using the main adder (#189) 5 years ago
divider.vhdl execute1: Remember dest GPR, RC, OE, XER for slow operations 5 years ago
divider_tb.vhdl Exit cleanly from testbench on success 5 years ago
dmi_dtm_dummy.vhdl Fix build issue in dmi_dtm_dummy.vhdl 5 years ago
dmi_dtm_tb.vhdl ram: Rework main RAM interface 5 years ago
dmi_dtm_xilinx.vhdl Don't reset JTAG request register asynchronously 5 years ago
dram_tb.vhdl litedram: Test bench 5 years ago
execute1.vhdl core: Do addpcis using the main adder (#189) 5 years ago
fetch1.vhdl Merge branch 'mmu' 5 years ago
fetch2.vhdl Merge branch 'mmu' 5 years ago
glibc_random.vhdl Reformat glibc_random 5 years ago
glibc_random_helpers.vhdl Reformat glibc_random 5 years ago
gpr_hazard.vhdl execute: Implement bypass from output of execute1 to input 5 years ago
helpers.vhdl execute: Copy XER[SO] to CR for cmp[i] and cmpl[i] instructions 5 years ago
icache.vhdl icache: Fix icbi potentially clobbering the icache (#192) 5 years ago
icache_tb.vhdl icache: Fix icbi potentially clobbering the icache (#192) 5 years ago
icache_test.bin icache_tb: Improve test and include test file 5 years ago
insn_helpers.vhdl Implement the addpcis instruction 5 years ago
loadstore1.vhdl MMU: Implement reading of the process table 5 years ago
logical.vhdl execute: Move popcnt and prty instructions into the logical unit 5 years ago
microwatt.core litedram: Add an L2 cache with store queue 5 years ago
mmu.vhdl MMU: Implement reading of the process table 5 years ago
multiply.vhdl execute1: Remember dest GPR, RC, OE, XER for slow operations 5 years ago
multiply_tb.vhdl Exit cleanly from testbench on success 5 years ago
plru.vhdl plru: Improve sensitivity list 5 years ago
plru_tb.vhdl Exit cleanly from testbench on success 5 years ago
ppc_fx_insns.vhdl sprs: Store common SPRs in register file 5 years ago
register_file.vhdl debug: Provide a way to examine GPRs, fast SPRs and MSR 5 years ago
rotator.vhdl Implement the extswsli instruction 5 years ago
rotator_tb.vhdl Exit cleanly from testbench on success 5 years ago
sim_bram.vhdl ram: Rework main RAM interface 5 years ago
sim_bram_helpers.vhdl ram: Rework main RAM interface 5 years ago
sim_bram_helpers_c.c Consolidate VHPI code 5 years ago
sim_console.vhdl Reformat sim_console 5 years ago
sim_console_c.c Consolidate VHPI code 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 Consolidate VHPI code 5 years ago
sim_uart.vhdl Wire up sim uart TX interrupt 5 years ago
sim_vhpi_c.c Consolidate VHPI code 5 years ago
sim_vhpi_c.h Consolidate VHPI code 5 years ago
soc.vhdl litedram: Add support for booting without BRAM 5 years ago
sync_fifo.vhdl litedram: Add an L2 cache with store queue 5 years ago
syscon.vhdl litedram: Add support for booting without BRAM 5 years ago
utils.vhdl litedram: Add support for booting without BRAM 5 years ago
wishbone_arbiter.vhdl wb_arbiter: Early master selection 5 years ago
wishbone_bram_tb.bin ram: Rework main RAM interface 5 years ago
wishbone_bram_tb.vhdl Exit cleanly from testbench on success 5 years ago
wishbone_bram_wrapper.vhdl Add log2ceil and use it in bram code 5 years ago
wishbone_debug_master.vhdl wishbone_debug_master: Fix address auto-increment for memory writes 5 years ago
wishbone_types.vhdl soc: Rework interconnect 5 years ago
writeback.vhdl execute1: Simplify the interrupt logic a little 5 years ago
xics.vhdl irq: Simplify xics->core irq input 5 years ago

README.md

Microwatt

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

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. You may need to set the CROSS_COMPILE environment variable to the prefix used for your cross compilers. The default is powerpc64le-linux-gnu-.
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.

  • Next build microwatt:

git clone https://github.com/antonblanchard/microwatt
cd microwatt
make

To build using Docker:

make DOCKER=1

and to build using Podman:

make PODMAN=1
  • 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=16384 --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)