SVN for VLSI Engineers

1 SVN vs Git — Key Differences

If you're coming from Git, understanding SVN's different model prevents confusion. If SVN is your first VCS, it is simpler to learn but less flexible for parallel work.

2 SVN Concepts & Repository Layout

By convention, every SVN repository has a standard three-directory layout at its root:

svn://server/chip_project/
├── trunk/        # main development line (like 'main' in Git)
│   ├── rtl/
│   ├── constraints/
│   ├── scripts/
│   └── tb/
├── branches/     # feature and release branches
│   ├── cdc_fix/
│   └── release_v1.2/
└── tags/         # immutable snapshots for tapeout / releases
    ├── tapeout_v1.0/
    └── tapeout_v2.0/

• trunk: The main integration line. Equivalent to Git's main branch. Stable, working RTL lives here.
• branches: Copies of trunk for parallel development, CDC fixes, or customer-specific variants.
• tags: Read-only snapshots of a specific revision — created at tapeout, tape-in, or milestone delivery. Never modify a tag.
• Revision numbers: Every commit increments a single global counter for the entire repository — r1001, r1002. This makes it easy to reference a specific state: "the RTL at r4532."

3 Checkout & Working Copy

# Check out the full trunk
svn checkout svn://server/chip_project/trunk chip_project

# Check out only the RTL directory (partial checkout — SVN superpower)
svn checkout svn://server/chip_project/trunk/rtl rtl

# Check out via HTTP/HTTPS
svn checkout https://svn.company.com/repos/chip/trunk chip

# Check out a specific revision
svn checkout svn://server/chip_project/trunk@4532 chip_r4532

# Check out a branch
svn checkout svn://server/chip_project/branches/cdc_fix cdc_fix

# Show working copy information (URL, revision, status)
svn info

# Show info for a specific file
svn info rtl/fifo_ctrl.sv

4 Daily Workflow

Check Status and Update

# Check what's modified in your working copy
svn status
# M = Modified, A = Added, D = Deleted, ? = Unversioned, C = Conflict

# Fetch latest changes from server
svn update

# Update a single file
svn update rtl/top.sv

# Update to a specific revision
svn update -r 4532

Making Changes

# Edit a file — SVN does NOT require locking before editing (unless lock-modify-unlock is enforced)
vim rtl/fifo_ctrl.sv

# Add a new file to version control
svn add rtl/new_module.sv

# Add a new directory recursively
svn add tb/new_test/

# Schedule a file for deletion
svn delete rtl/old_module.sv

# Move/rename a file (preserves history)
svn move rtl/fifo.sv rtl/fifo_ctrl.sv

# Copy a file (creates a versioned copy with history link)
svn copy rtl/alu_v1.sv rtl/alu_v2.sv

Reviewing and Committing

# See what will be committed
svn diff

# Diff a specific file
svn diff rtl/fifo_ctrl.sv

# Commit ALL modified files
svn commit -m "Fix setup timing violation in fifo_ctrl — add pipeline stage"

# Commit specific files only
svn commit rtl/fifo_ctrl.sv constraints/top.sdc -m "CDC fix: 2FF synchronizer added"

# Revert a file to the last committed state
svn revert rtl/top.sv

# Revert entire working copy
svn revert -R .

5 Branching & Tagging

In SVN, branches and tags are both just directory copies in the repository. The difference is convention — tags are never modified after creation.

Creating a Branch

# Create a branch from trunk HEAD
svn copy svn://server/chip/trunk \
         svn://server/chip/branches/cdc_rework \
         -m "Branch for CDC synchronizer rework"

# Create a branch from a specific revision (e.g., the state before a bad commit)
svn copy svn://server/chip/trunk@4530 \
         svn://server/chip/branches/hotfix_r4530 \
         -m "Hotfix branch from r4530"

# Switch your working copy to a branch
svn switch svn://server/chip/branches/cdc_rework

Creating a Tag (Tapeout Snapshot)

# Tag the current trunk at tapeout
svn copy svn://server/chip/trunk \
         svn://server/chip/tags/tapeout_v2.0 \
         -m "Tapeout v2.0 — DC synthesis WNS=-0.01ns, all DRC clean"

# Tag a specific revision
svn copy svn://server/chip/trunk@5200 \
         svn://server/chip/tags/freeze_pre_eco \
         -m "Pre-ECO freeze at r5200"

6 Merging Branches

SVN tracks merge history since version 1.5. Use svn merge to bring branch changes back to trunk.

# 1. Switch to trunk working copy
svn switch svn://server/chip/trunk

# 2. Update to latest
svn update

# 3. Merge all changes from the branch into working copy
svn merge svn://server/chip/branches/cdc_rework

# 4. Review the result
svn status
svn diff

# 5. Resolve any conflicts (see below), then commit the merge
svn commit -m "Merge cdc_rework branch — 2FF synchronizers added to all CDC crossings"

# Merge a specific revision range only
svn merge -r 4550:4560 svn://server/chip/branches/cdc_rework

# Preview what will be merged (dry run)
svn merge --dry-run svn://server/chip/branches/cdc_rework

Resolving Conflicts

# SVN marks conflicts with extra files:
# top.sv        — the conflicted file (contains <<<< ==== >>>> markers)
# top.sv.mine   — your version
# top.sv.rOLD   — original base
# top.sv.rNEW   — incoming version

# After manually editing top.sv to resolve:
svn resolve --accept working rtl/top.sv

# Accept their version (discard yours)
svn resolve --accept theirs-full rtl/top.sv

# Accept your version (discard incoming)
svn resolve --accept mine-full rtl/top.sv

# List all conflicted files
svn status | grep ^C

7 svn:externals — Shared IP Blocks

SVN externals are one of its most useful features for VLSI projects. An external lets you include a subdirectory from a different repository path (or even a different revision) inside your working copy — automatically, without copying files. This is the standard way to share verified IP blocks across multiple chip projects.

Setting Up Externals

# Example: Your SoC project wants to include a shared UART IP at a specific revision

# Edit the svn:externals property on the ip/ directory
svn propedit svn:externals ip/

# In the editor, add one external per line:
# local_dir   [-r REV]   URL
uart_ip    -r 1234    svn://server/shared_ip/trunk/uart
i2c_ip     -r 5678    svn://server/shared_ip/trunk/i2c
pll_model              svn://server/shared_ip/tags/pll_v2.1

# Save and close. Commit the property change.
svn commit -m "Add uart and i2c externals at validated revisions"

# Now svn update populates ip/uart_ip, ip/i2c_ip, ip/pll_model automatically
svn update

Viewing and Managing Externals

# Show all externals defined in working copy
svn propget svn:externals -R .

# Show externals status separately
svn status --show-updates

# Update only a specific external
svn update ip/uart_ip

8 SVN Properties & Keywords

SVN properties are metadata attached to files or directories. Two properties are especially useful for RTL files.

svn:keywords — Auto-insert Revision Info

# Enable keyword substitution on a file
svn propset svn:keywords "Id Rev Author Date" rtl/top.sv

# Then add a comment line in the file:
// $Id$              — expands to: filename, revision, date, author
// $Rev$             — expands to just the revision number
// $Author$          — expands to committing username
// $Date$            — expands to commit timestamp

# After commit, the comment automatically becomes:
// $Id: top.sv 4532 2025-05-12 09:34:11Z jsmith $

svn:ignore — Per-directory Ignore Patterns

# Set ignore patterns for a directory
svn propedit svn:ignore .

# Add patterns (one per line):
*.log
*.rpt
work/
*.ddc
*.wlf
*.vcd
WORK/

# Commit the ignore property
svn commit -m "Add svn:ignore for EDA output files"

# Check what's being ignored
svn status --no-ignore | grep ^I

9 History, Log & Blame

# Show commit log for the working copy
svn log

# Compact one-line-ish log (limit to 20 entries)
svn log -l 20

# Log for a specific file
svn log rtl/fifo_ctrl.sv

# Log with diff (shows actual changes)
svn log -v --diff rtl/fifo_ctrl.sv -l 5

# Log between two revisions
svn log -r 4500:4600

# Search log messages
svn log | grep -A 3 "CDC"

# Show who changed each line (blame)
svn blame rtl/alu.sv

# Blame a specific revision of a file
svn blame -r 4532 rtl/alu.sv

# Show diff between two revisions
svn diff -r 4500:4600 rtl/fifo_ctrl.sv

# Show diff between a revision and current working copy
svn diff -r 4532 rtl/top.sv

# Show file content at a specific revision
svn cat -r 4532 rtl/top.sv

10 Quick Reference

11 Q&A