renode-dpi-examples

Copyright (c) 2023 Antmicro

Example integration between Renode and a Verilog model using DPI (SystemVerilog Direct Programming Interface) calls.

All samples are intended to work in both Verilator and Questa simulators. This repository contains a CI configured to build and run samples in Verilator. Looking at the CI configuration is a good way to reproduce an example, but you can follow the instructions below, especially if you use Questa.

Architecture

Renode communicates with the simulator over TCP using a dedicated protocol. The library which implements this protocol can be found in Renode sources. It's mainly written in C++, but there is an additional wrapper written in SystemVerilog, which uses DPI calls to interact with the API written in C++.

The HDL top simulation file contains Renode related snippets:

• code initializing a connection (with ports and IP address passed from parameters of a module)
• code creating modules and interfaces of busses
• code resetting a bus
• code used to receive and handle messages

Note
The code intentionally blocks the elapse of the simulation time while waiting for a message.

Usage of prebuilt example

Preparing Renode

The rest of this instruction assumes you have Renode in the renode directory inside this repository. You just need to download and extract it, and install dependencies for the Robot test framework. Follow the steps below.

Linux

Run commands

wget --progress=dot:giga https://builds.renode.io/renode-latest.linux-portable.tar.gz
mkdir renode
tar -xf renode-latest.linux-portable.tar.gz --strip-components 1 -C renode
python3 -m pip install -r renode/tests/requirements.txt

Windows

• Download the Renode nightly package
• Extract it to the renode directory
• Run python -m pip install -r renode/tests/requirements.txt

Running Linux on Zynq-7000 with verilated FastVDMA

Run one of the commands below. It will start Renode and show two windows:

• Monitor which can be used to manage a simulation
• UART analyzer with terminal for interaction with Linux on Zynq-7000

This sample uses a prebuilt executable of a verilated FastVDMA controller. You can build the executable by yourself from the sample directory.

Linux

renode/renode -e start samples/axi_fastvdma_prebuilt/platform.resc

Windows

renode\bin\Renode.exe -e start samples\axi_fastvdma_prebuilt\platform.resc

Manual compilation

Building Verilator

For simplicity, build Verilator in the verilator directory inside this repository to use unmodified commands from this README.
Instead of building Verilator from source you can download the artifacts with Verilator, which is built on the CI. You can find it in a specific run listed on the Actions page.

Linux (Ubuntu)

Use command below to build Verilator.

sudo apt-get update && sudo apt-get install git help2man perl python3 make autoconf g++ flex bison ccache libgoogle-perftools-dev numactl perl-doc libfl2 libfl-dev zlibc zlib1g zlib1g-dev
git clone https://github.com/verilator/verilator.git
cd verilator
git checkout v5.018
autoconf
./configure
make -j `nproc`

Preparing Renode

You can find an instruction on preparing Renode in the previous section.

Building a sample

Linux

Run in samples/axi_ram

mkdir build
cd build
cmake .. -DUSER_RENODE_DIR=../../../renode -DUSER_VERILATOR_DIR=../../../verilator
make

Note
Instead of using -D arguments you can set RENODE_ROOT or VERILATOR_ROOT environmental variables.
You may use a path to installed packages in both approaches i.e. export RENODE_ROOT=/opt/renode or -DUSER_RENODE_DIR=/opt/renode

Windows

To build a sample on Windows you need the dependencies listed below:

• mingw32-make.exe
• CMake

A lot of MinGW toolchains contain required tools. The one of approaches is to download the WinLibs archive, extract it and add to the PATH enviromental variable.

Run in CMD in samples/axi_ram

mkdir build
cd build
cmake.exe .. -G "MinGW Makefiles" -DUSER_RENODE_DIR="..\..\..\renode" -DUSER_VERILATOR_DIR="..\..\..\verilator"
mingw32-make.exe

Testing

There are tests for Verilator, Questa and VCS. If the cosimulation block executable is not found for some of them, the corresponding tests will be skipped.

To run tests, do the following from the repository root:

Linux

renode/renode-test samples/axi_ram/tests.robot

Windows

renode\bin\renode-test.bat samples\axi_ram\tests.robot --variable=VERILATED_BINARY:samples\axi_ram\build\verilated.exe

Running a sample manually

Instead of run an automatic test using the Robot Framework, you can manually run Renode and an external simulator.

Starting Renode

To run Renode with the RESC script, which creates a platform, just execute one of the following commands in the repository root:

• renode/renode samples/axi_ram/platform.resc on Linux
• renode\bin\Renode.exe samples\axi_ram\platform.resc on Windows

Renode communicates with a simulator over sockets and you will need communication parameters. Run the mem ConnectionParameters command in the Monitor.

The output of the command consists of:

• the receiver port (later referenced to as <ReceiverPort>),
• the sender port (later referenced to as <SenderPort>),
• the IP address (later referenced to as <Address>).

You will need to substitute placeholders in the following commands which use these parameters.

Connecting to a simulator

You can use one of the following command to start the simulator and pass connection parameters:

• samples/axi_ram/build/verilated <ReceiverPort> <SenderPort> <Address> for Verilator on Linux
• samples\axi_ram\build\verilated.exe <ReceiverPort> <SenderPort> <Address> for Verilator on Windows
• vsim design_optimized -work samples/axi_ram/build/work_questa -do "run -all" -GReceiverPort=<ReceiverPort> -GSenderPort=<SenderPort> -GAddress=\"<Address>\" for Questa on Linux
• vsim design_optimized -work samples\axi_ram\build\work_questa -do "run -all" -GReceiverPort=<ReceiverPort> -GSenderPort=<SenderPort> -GAddress=\`"<Address>\`" -ldflags -lws2_32 in Powershell for Questa on Windows

After starting the simulator establish a connection by executing the mem Connect command in the Renode Monitor. No output indicates that Renode and the simulator are successfully connected.

Note
Questa may not be responsive during simulation.
Instead of passing the -do "run -all" argument to Questa you may execute the run -all command in the transcript window.

Interacting with the design

You can simply try the prepared setup by running the following commands in the Renode.

mem WriteDoubleWord 0x10 0x12345678
mem ReadDoubleWord 0x10

You can close the simulation by calling the quit command in the Renode Monitor. It will also finish the HDL simulation.

Samples list

Sample name	Function Description
AXI RAM	AXI4 Subordinate
DMATop (the FastVDMA controller)	AXI4-Lite Subordinate, AXI4 Manager, GPIO
AHB Memory	AHB Subordinate
Simple AHB DMA	AHB Subordinate, AHB Manager, GPIO
Simple AHB Manager	AHB Manager
APB3 Completer Memory	APB3 Completer
APB3 Requester Synthesizable	APB3 Requester
APB3 Standalone Simulation	APB3 Requester, APB3 Completer, without DPI usage