【Semiconductor】🧱 23. OpenLane Is 90% About the Environment
WSL2, Docker, and PDK Pitfalls You Must Avoid
topics: [“OpenLane”, “ASIC”, “EDA”, “Docker”, “WSL”]
🧭 Introduction: Why Does OpenLane “Not Work”?
OpenLane is an open-source ASIC design flow that enables a full pipeline
from RTL to GDSII.
🔗 Official repository:
https://github.com/The-OpenROAD-Project/OpenLane
Despite this, users frequently report the following issues:
- ❌ Installation fails
- ❌ The flow stops halfway
- ❌ It worked yesterday, but is broken today
- ❌ The tutorial was followed exactly, yet synthesis fails
Let us start with the conclusion.
⚠️ 90% of OpenLane problems are caused by the environment.
Before blaming RTL or constraints,
the environment itself is often already broken.
This article is based on
Phase 1: Environment Survival of the OpenLane Guide, and explains—
with reasons, not procedures—
- 🧱 Why the order must never be skipped
- 🔀 Why OpenLane1 and OpenLane2 must be separated
- 📦 Why the PDK must be fixed
📘 The original structured guide is available here:
https://samizo-aitl.github.io/openlane-guide/
🧩 OpenLane Is Not a “Tool” — It Is an Environment
This mindset is essential.
OpenLane is not a single tool.
It is a tightly coupled environment consisting of:
- 🧠 Yosys (logic synthesis)
- 🏗 OpenROAD (placement & routing)
- 🧪 Magic / Netgen (DRC / LVS)
- ⏱ STA / Tcl / Python / Make
All of these are integrated inside Docker containers.
Therefore:
💥 When OpenLane breaks,
it means something in WSL × Docker × Host OS × PDK is broken.
🐳 WSL2 + Docker Desktop Is Not a Compromise
Common misconceptions include:
- 🤔 “Wouldn’t native Linux be faster?”
- 🤔 “Is Docker really necessary?”
These are the first traps beginners fall into.
Why WSL2 + Docker?
There are three reasons:
- 🧼 To eliminate host OS differences
- 🧨 To contain dependency chaos
- ♻️ To operate under the assumption that environments are disposable
OpenLane environments are not meant to be grown long-term.
🔁 Reproducible containers that can be recreated at any time
WSL2 + Docker Desktop fits this philosophy perfectly.
🔀 Mixing OpenLane1 and OpenLane2 Will Break Everything
This is the most common and most destructive failure point.
Fundamentally Different Design Philosophies
| Item | OpenLane1 | OpenLane2 |
|---|---|---|
| 🎯 Purpose | Stable operation | Experimentation |
| 🧭 Flow | Makefile-based | Python-based |
| 📦 PDK | Fixed | Variable |
| ♻️ Reproducibility | High | Low |
They are not designed to coexist.
If they share the same WSL, Docker setup, or PDK path,
🚨 failure is guaranteed.
“After testing OpenLane2, OpenLane1 stopped working.”
This is not a bug.
It is the expected outcome.
📦 Using the “Latest” PDK Is the Worst Choice
Beginners often say:
✨ “I want to use the latest PDK.”
This is a fatal mistake.
A PDK Is a Massive Set of Assumptions
A PDK is not just data.
It defines:
- ⚡ SPICE models
- 📐 LEF / DEF
- ⏱ Timing models
- 🧪 DRC rules
Changing the PDK means:
🔄 All design assumptions change.
The Only Correct Rule
- 📌 Fix the PDK
- 🔗 Fix it together with the OpenLane version
- 🧪 Test updates only in separate environments
Without this discipline,
reproducibility is impossible, especially for CI or education.
⚖️ Broken Environments vs. Stable Environments
💣 Characteristics of Broken Environments
- OpenLane1 and 2 mixed together
- PDK updated mid-project
- Docker images treated as persistent assets
- No environment export
🛡 Characteristics of Stable Environments
- Clear separation by purpose
- Fixed PDK
- Disposable Docker containers
- Export / Import as standard practice
💾 WSL Export / Import Is Not a Backup
WSL Export / Import is not disaster recovery.
🔑 It is a required operational mechanism.
- 📤 Export when the environment works
- 🧪 Export before experiments
- 📥 Import immediately when broken
Ignoring this guarantees eventual failure.
🧱 Why the Order Must Never Be Skipped
The OpenLane Guide strictly enforces order for a reason.
❗ If the environment is broken,
physical design and timing analysis are meaningless.
📝 Summary
- 🧠 OpenLane is 90% environment
- 🐳 WSL2 + Docker is mandatory
- 🔀 OpenLane1 and OpenLane2 must be separated
- 📦 PDK must be fixed
- 💾 Export / Import is part of normal operation
This is the conclusion of
Phase 1: Environment Survival.
▶️ Next Article
Next is Phase 2: Physical Design Reality.
- 🏗 Why automated flows fail
- ⏱ Why timing suddenly collapses
- 👀 What you must inspect in the GUI
OpenLane is not magic.
We will expose the physical reality behind the automation.