riscv-mini

Author: Donggyu Kim (dgkim@eecs.berkeley.edu)

riscv-mini is a simple RISC-V 3-stage pipeline written in Chisel. It has been a crucial example in various project developments, including Chisel3, FIRRTL, Strober, simulation and verification methodologies. It implements RV32I of the User-level ISA Version 2.0 and the Machine-level ISA of the Privileged Architecture Version 1.7. Unlike other simple pipelines, it also contains simple instruction and data caches.

Note that a real-world processor is not the goal of riscv-mini. It is developed as an intermediate example before diving into rocket-chip.

Datapath Diagram

Getting Started

$ git clone https://github.com/ucb-bar/riscv-mini.git
$ cd riscv-mini
$ make            # generate firrtl & verilog files in generated-src

The verilog output file can be used for verilator simulation or the ASIC tool flow.

Running Verilator Simulation

First, generate the verilator binary:

$ make verilator

This will generate VTile in the top-level directory.

Now, you can run verilator simulation for a given hex file as follows:

$ ./VTile <hex file> [<vcd file> 2> <log file>]

<vcd file> and the pipe to <log file> are optional. The waveform is dumped to dump.vcd and the execution trace is printed in the screen by default.

The following command runs the whole test hex files in verilator and dumps the traces and the waveforms to the 'outputs' directory:

$ make run-tests

Unit and Integration Tests with `sbt`

riscv-mini provides synthesizable unit & integration tests. Theres are six sets of unit tests(ALUTests, BrCondTests, ImmGenTests, CSRTests, CacheTests, DatapathTests), running user-defined test vectors. To execute them, first launch sbt with make sbt and run:

> testOnly mini.[testname]

There are also six sets of integration tests, running the hex files from riscv-tests. To execute them, also launch sbt and run:

> testOnly mini.[Core|Tile][Simple|ISA|Bmark]Tests

Core only contains the datapath and the control unit, while Tile also contains I$ and D$. Simple only runs rv32ui-p-simple, ISA runs the whole ISA tests, and Bmark runs five benchmarks(median, multiply, qsort, towers, vvadd). Note that all tests in a set run in parallel.

Finally, to run all the tests, just in sbt:

> test

Running Your Own Program on `riscv-mini`

At this point, you may want to implement and exeucte your custom application on riscv-mini. In this case, you need to install RISC-V tools for priv 1.7. This repo provides a script to install the correct version of tools. Run the script as follows:

$ export RISCV=<path to riscv tools for priv 1.7>
$ ./build-riscv-tools

It takes a while to install the toolchain, so please be patient.

This repo also provides a template for your own program in custom-bmark. Add your c or assembly code and edit Makefile. Next, to compile you program, run make in custom-bmark to generate the binary, dump, and the hex files. Finally, run the following command in the base directory:

$ make run-custom-bmark

noloerino/riscv-mini