Quick start

Overview

OpenLane is an automated RTL to GDSII flow based on several components including OpenROAD, Yosys, Magic, Netgen, CVC, SPEF-Extractor, CU-GR, Klayout and a number of custom scripts for design exploration and optimization. The flow performs full ASIC implementation steps from RTL all the way down to GDSII.

The tool encapsulates the underlying tools to allow engineers to configure them all in one place: config.tcl. This file contains assignments to the variables that flow uses.

The rest of the tutorial assumes OpenLane installation has been complete.

Entering the OpenLane environment

Note

If you installed OpenLane following local installation steps, then you are on your own.

OpenLane uses Docker to create reproducible environment for your projects. You don’t need any extra steps to run the Docker image, as Makefile already takes care of it. Just run following command to enter OpenLane environment:

make mount

Creating new designs

Warning

This guide assumes that you are running inside Docker image. If you are not running inside docker that run make mount before following steps below you are on your own

First, start OpenLane Docker image using following command:

make mount

The ./flow.tcl is the entry point for OpenLane. This script is used to run the flow, run the interactive sessions, select the configuration and create OpenLane design files.

To add a new design, the following command creates a configuration file for your design:

./flow.tcl -design <design_name> -init_design_config

This will create the following directory structure:

designs/<design_name>
├── config.tcl

config.tcl is a global configuration for all PDKs. For more information about design configuration files please visit this page. In the configuration file, you should edit the required variables and the optional variables, if needed.

The design_name could be replaced by the design_directory, which will allow you to run any design on your machine.

It is recommended to place the design’s verilog files in a src directory inside the design’s folder as following:

designs/<design_name>
├── config.tcl
├── src
│   ├── design.v

However, you can point to the source files while initializing the design and they will be pointed to automatically in the configuration file and will also be automatically copied to the src directory creating the same structure shown above.

./flow.tcl -design <design_name> -init_design_config -src <list_verilog_files>

This is typical structure of the design folder:

.
├── config.tcl
├── runs
│   └── RUN_2022.06.24_16.52.13
│       ├── cmds.log
│       ├── config.tcl
│       ├── logs
│       ├── openlane.log
│       ├── OPENLANE_VERSION
│       ├── PDK_SOURCES
│       ├── reports
│       ├── results
│       ├── runtime.yaml
│       ├── tmp
│       └── warnings.log
└── src
    └── mem_1r1w.v

Main files are config.tcl and src/ folder that contains source code.

You can find more information regarding the ./flow.tcl in the documentation here. And here is the reference documentation regarding the configuration valirables.

Running the flow

In order to run the flow you need to execute following commands:

./flow.tcl -design <design_name>

This will run the flow for design <design_name>.

Now that you know how to run the flow for your design, let’s actually take a deep dive into real life example.

Advanced: Using custom PDK locations and Docker images

Warning

If you accidently used wrong version of PDK or OpenLane docker image then you might have significant issues down the line. Avoid overwriting PDK on your own or using different OpenLane images, if you don’t know what are you doing then do not set any of those variable.

While this is not recommended, if you need to overwrite the location of PDK, then set the environment variable PDK_ROOT before running make mount. Another environment variable is OPENLANE_IMAGE_NAME. It can be used to overwrite the Docker image that will be used but by default it’s dynamically obtained using your current git version. Both PDK_ROOT and OPENLANE_IMAGE_NAME can be set independently. Example for setting both variables:

export PDK_ROOT=/opt/pdks
export OPENLANE_IMAGE_NAME=efabless/openlane:ebad315d1def25d9d253eb2ec1c56d7b4e59d7ca
make mount

Keep in mind, that if tool is unable to recognize the git commit, you might want to update the git, not set OPENLANE_IMAGE_NAME variable.

Advanced: Installing other Standard Cell Libraries

Follow the guide on this page