| id | dv-coverage-closure |
| name | S10 — DV Coverage Closure |
| version | 1.0 |
| description | Analyses VCS urg coverage reports (code + functional), identifies gaps, suggests test stubs or exclusions, generates .el exclusion files, evaluates per-milestone closure criteria, and produces a combined sign-off HTML report integrating S7 (assertions), S9 (regression), and S10 (coverage) data.
|
| inputs | {"required":["merged.vdb (from S9 dv-regression)","dv_regression_data.json (from S9)","dv_assertions_data.json (from S7)"],"optional":["coverage_config.yaml (thresholds + exclusion patterns)"]} |
| outputs | ["dv_coverage_data.json","exclusions/combined.el (+ per-type .el files)","stubs/tests/*.sv, stubs/sequences/*.sv","signoff_report/index.html","milestone_results.json"] |
| scripts | ["skills/common/scripts/parse_coverage_report.py","skills/common/scripts/generate_coverage_closure.py","skills/common/scripts/gen_coverage_signoff_report.py","skills/common/scripts/check_environment.py"] |
| tags | ["coverage","urg","sign-off","closure","functional-coverage","code-coverage","exclusions"] |
S10 — DV Coverage Closure
Overview
S10 is the final DV skill. It consumes outputs from S7 (assertion CHK_IDs) and S9 (regression logs, merged coverage VDB) to analyse coverage gaps, guide the engineer through exclusion/stub decisions, and produce a formal sign-off report.
Prerequisite skills: S7 (dv-assertions) and S9 (dv-regression) must have run first.
Step 1 — Validate Prerequisites and Environment
Check that all required inputs exist before proceeding.
1a Environment check
python3 skills/common/scripts/check_environment.py --skill s10
Required tools: urg (VCS coverage merge), vcs on PATH. No pip dependencies.
1b Locate required files
Search the project dv/ directory for:
| File | Source Skill | Required |
|---|
dv/sim/regression/*/merged.vdb | S9 | YES |
dv/sim/results/dv_regression_data.json | S9 | YES |
dv/dv_assertions_data.json | S7 | YES |
dv/sim/regression/coverage_config.yaml | Manual or auto-generated | NO (defaults used) |
If merged.vdb or dv_regression_data.json is missing, STOP and print:
✗ S10 requires S9 regression outputs.
→ Run S9 (dv-regression) first: it generates merged.vdb and dv_regression_data.json.
→ If you have an existing VDB, set the path manually in coverage_config.yaml.
If dv_assertions_data.json is missing, continue but note that assertion cross-reference will be skipped.
1c Write default coverage_config.yaml (if not present)
thresholds:
dv_i:
line_pct: 80.0
toggle_pct: 70.0
branch_pct: 75.0
expression_pct: 70.0
functional_pct: 60.0
regression_pass: 90.0
dv_c:
line_pct: 95.0
toggle_pct: 90.0
branch_pct: 95.0
expression_pct: 90.0
functional_pct: 85.0
regression_pass: 98.0
dv_f:
line_pct: 99.0
toggle_pct: 95.0
branch_pct: 99.0
expression_pct: 99.0
fsm_pct: 99.0
functional_pct: 99.0
regression_pass: 100.0
auto_exclude_patterns:
- ".*_dft_.*"
- ".*_tb_.*"
- ".*vendor_ip.*"
- ".*_unused.*"
- ".*_tie.*"
- ".*_dummy.*"
Step 2 — Generate Fresh urg Text Reports
Re-run urg to produce machine-parseable text reports from merged.vdb.
urg -full64 -dir <merged.vdb> \
-report <output_dir>/urgReport \
-format text \
-l <output_dir>/urg_run.log
urg -full64 -dir <merged.vdb> \
-report <output_dir>/urgReport_html \
-format html
Key output files parsed in subsequent steps:
urgReport/dashboard.txt — top-level per-type summaryurgReport/hier.txt — per-instance code coverage hierarchyurgReport/groups.txt — functional coverage covergroup bins
If hier.txt or groups.txt are missing after urg runs, print a warning and skip the affected parse step.
Step 3 — Parse Code Coverage
Parse urgReport/hier.txt for line, toggle, branch, expression, and FSM coverage.
python3 skills/common/scripts/parse_coverage_report.py \
--mode code \
--hier <output_dir>/urgReport/hier.txt \
--out <output_dir>/gaps/code_gaps.json
What this produces:
For each instance in the hierarchy, extract:
- Module name and instance path
- Per-type: covered count, total count, coverage percentage
- For gaps (< threshold): list of uncovered items with file path, line number, detail description
Display a code coverage summary table after parsing:
Code Coverage Summary
─────────────────────────────────────────────────────────────
Type Covered Total Pct DV-F Thr Delta
─────────────────────────────────────────────────────────────
Line 1240 1250 99.2% 99.0% +0.2% ✓
Toggle 890 980 90.8% 95.0% -4.2% ✗
Branch 430 440 97.7% 99.0% -1.3% ✗
Expression 210 215 97.7% 99.0% -1.3% ✗
FSM 48 50 96.0% 99.0% -3.0% ✗
─────────────────────────────────────────────────────────────
Total code gaps requiring attention: 23
Step 4 — Parse Functional Coverage
Parse urgReport/groups.txt for covergroup bins.
python3 skills/common/scripts/parse_coverage_report.py \
--mode functional \
--groups <output_dir>/urgReport/groups.txt \
--out <output_dir>/gaps/func_gaps.json
What this produces:
For each covergroup/coverpoint/bin:
- Hit count, at_least count, covered/uncovered status
- Full bin path:
scope::covergroup::coverpoint::bin_name
Ignore: ignore_bins, illegal_bins, bins with at_least 0 (weight-zero).
Display a functional coverage summary:
Functional Coverage Summary
─────────────────────────────────────────────────────────────
Covergroup Bins Hit Missed Coverage
─────────────────────────────────────────────────────────────
cg_apb_register 12 10 2 83.3%
cg_uart_tx 20 15 5 75.0%
cg_uart_rx 8 8 0 100.0% ✓
─────────────────────────────────────────────────────────────
Total: 40 bins, 33 covered, 7 uncovered (82.5%)
Step 5 — Cross-reference with Assertions (S7 data)
If dv_assertions_data.json is present, annotate each gap:
- Check if the gap's instance path matches any assertion module
- Check if the gap's signal/line is exercised by a
cover property statement
- Tag
assertion_backed: true for gaps already proven via formal or SVA coverage
Assertion-backed gaps are strong exclusion candidates — they have functional correctness verified by another mechanism even if code coverage is not driven.
Step 6 — Classify Gaps
Classify each gap as:
| Class | Meaning | Default Action |
|---|
excludable | Unreachable, tool-generated, DFT, vendor IP, assertion-backed | Offer exclusion |
coverable | Reachable logic with no existing test stimulus | Offer test stub |
requires_analysis | Cross-coverage, parameterised logic, complex FSM | Ask user |
Classification uses auto_exclude_patterns from coverage_config.yaml plus these rules:
- Toggle of
tie_*, unused_*, one_*, zero_* signals → excludable
- FSM state reachable only during reset →
excludable if rst_n in state condition
- Functional bin with value combination outside DUT spec →
excludable
- Uncovered branch in
generate block with fixed parameters → excludable
Print gap count by class before interactive step.
Step 7 — Interactive Gap Resolution
Walk through each gap and ask the user to decide: exclude, generate stub, or skip.
Gap Resolution (23 gaps total: 14 excludable, 7 coverable, 2 requires-analysis)
────────────────────────────────────────────────────────────────────────────────
[GAP 1/23] Type: Toggle Class: EXCLUDABLE
Instance : tb_top.dut.u_ctrl.gen_dft_logic
Signal : scan_en (0→1 direction)
File : rtl/ctrl.sv:142
Reason : Matches pattern '.*_dft_.*' — DFT-only logic
Draft exclusion:
EXCL_TOGGLE tb_top.dut.u_ctrl.gen_dft_logic scan_en 01 -comment "DFT scan enable, not driven in functional mode"
Accept? [Y=exclude / s=stub / n=skip] :
For coverable gaps:
[GAP 8/23] Type: Functional Class: COVERABLE
Bin : cg_uart_tx::cp_data_value::bin_0xFF
Scope : tb_top.dut.u_uart_tx
Hit count : 0 / 1
Suggestion: Add a test that sends UART byte 0xFF
Draft stub:
stubs/sequences/seq_uart_tx_0xff_coverage.sv
Generate stub? [Y=stub / e=exclude / n=skip] :
Batch mode (--non-interactive): accepts all suggested defaults automatically.
After all gaps resolved, print decision summary:
Decisions: 14 excluded, 7 stubs queued, 2 skipped
Step 8 — Generate Exclusion Files
Write .el files for all accepted exclusions.
python3 skills/common/scripts/generate_coverage_closure.py \
--mode exclusions \
--decisions <output_dir>/gaps/gap_decisions.json \
--out <output_dir>/exclusions/
Output files:
exclusions/
line_exclusions.el
toggle_exclusions.el
branch_exclusions.el
expression_exclusions.el
fsm_exclusions.el
functional_exclusions.el
combined.el ← concatenation of all above
.el file format (urg Synopsys standard):
// =============================================================================
// Exclusion File: toggle_exclusions.el
// Generated by: S10 dv-coverage-closure
// Date: 2026-03-22
// REVIEW REQUIRED before sign-off
// =============================================================================
EXCL_TOGGLE tb_top.dut.u_ctrl.gen_dft_logic scan_en 01
-comment "DFT scan enable, not driven in functional mode"
EXCL_FSM_STATE tb_top.dut.u_arb.fsm RESET_STATE
-comment "RESET_STATE only entered at power-on; excluded per design spec"
EXCL_COVBIN tb_top.dut.u_uart cg_uart_tx cp_parity bin_none
-comment "Parity disabled by UART_CTRL.PAR_EN=0 in all test configs"
Supported exclusion types:
EXCL_LINE <scope> <file> <line> -comment "..."EXCL_TOGGLE <scope> <signal> [01|10] -comment "..."EXCL_BRANCH <scope> <file> <line> <branch_idx> -comment "..."EXCL_EXPRESSION <scope> <file> <line> <expr_idx> <term_idx> -comment "..."EXCL_FSM_STATE <scope> <fsm> <state> -comment "..."EXCL_FSM_TRANS <scope> <fsm> <from> <to> -comment "..."EXCL_COVGROUP <scope> <group> -comment "..."EXCL_COVPOINT <scope> <group> <point> -comment "..."EXCL_COVBIN <scope> <group> <point> <bin> -comment "..."
Re-run urg with exclusions applied:
urg -full64 -dir <merged.vdb> \
-elfile exclusions/combined.el \
-report urgReport_excl \
-format text
Parse urgReport_excl/dashboard.txt and write coverage_after_exclusions.json.
Step 9 — Generate Test and Sequence Stubs
For each gap where the decision is "stub", generate a UVM .sv stub.
python3 skills/common/scripts/generate_coverage_closure.py \
--mode stubs \
--decisions <output_dir>/gaps/gap_decisions.json \
--tb-data dv/dv_tb_data.json \
--out <project_dv_dir>/
Stub structure for functional coverage gap:
// COVERAGE STUB — Generated by S10 dv-coverage-closure
// Gap ID : FUNC_GAP_003
// Target : cg_uart_tx::cp_data_value::bin_0xFF
// Scope : tb_top.dut.u_uart_tx
// Action : Drive UART TX byte value = 0xFF to hit this bin
// Status : NEEDS_ENGINEER_IMPLEMENTATION
// ─────────────────────────────────────────────────────────
class uart_tx_0xff_coverage_seq extends uart_vip_base_seq;
`uvm_object_utils(uart_tx_0xff_coverage_seq)
function new(string name = "uart_tx_0xff_coverage_seq");
super.new(name);
endfunction
task body();
uart_vip_seq_item txn;
// TODO: drive UART byte 0xFF to hit cg_uart_tx::cp_data_value::bin_0xFF
txn = uart_vip_seq_item::type_id::create("txn");
start_item(txn);
if (!txn.randomize() with { data == 8'hFF; })
`uvm_fatal("RAND", "Randomization failed")
finish_item(txn);
endtask
endclass
Stub structure for code coverage gap (FSM state / branch):
// COVERAGE STUB — Generated by S10 dv-coverage-closure
// Gap ID : CODE_GAP_007
// Target : tb_top.dut.u_arb.fsm — state STALL_STATE
// File : rtl/arb.sv:88
// Action : Drive stimulus that causes arbiter to enter STALL_STATE
// Status : NEEDS_ENGINEER_IMPLEMENTATION
// ─────────────────────────────────────────────────────────
class arb_stall_state_test extends apb_uart_base_test;
`uvm_component_utils(arb_stall_state_test)
function new(string name, uvm_component parent);
super.new(name, parent);
endfunction
task run_phase(uvm_phase phase);
// TODO: implement stimulus to reach arb FSM STALL_STATE
// Hint: arb.sv:88 — condition for entering STALL_STATE:
// (request_count > MAX_PENDING && ~grant_valid)
phase.raise_objection(this);
// ... stimulus here ...
phase.drop_objection(this);
endtask
endclass
Write stubs/stubs_manifest.json:
{
"generated_at": "...",
"stubs": [
{
"gap_id": "FUNC_GAP_003",
"stub_type": "sequence",
"file": "dv/sequences/uart/uart_tx_0xff_coverage_seq.sv",
"class_name": "uart_tx_0xff_coverage_seq",
"coverage_target": "cg_uart_tx::cp_data_value::bin_0xFF",
"status": "generated"
}
]
}
Step 10 — Milestone Closure Check
Evaluate per-milestone gates using post-exclusion coverage numbers.
python3 skills/common/scripts/generate_coverage_closure.py \
--mode milestone \
--coverage <output_dir>/coverage_after_exclusions.json \
--regression dv/sim/results/dv_regression_data.json \
--assertions dv/dv_assertions_data.json \
--config <output_dir>/coverage_config.yaml \
--out <output_dir>/milestone_results.json
Milestone gates evaluated:
| Metric | DV-I | DV-C | DV-F |
|---|
| Line coverage | ≥ 80% | ≥ 95% | ≥ 99% |
| Toggle coverage | ≥ 70% | ≥ 90% | ≥ 95% |
| Branch coverage | ≥ 75% | ≥ 95% | ≥ 99% |
| Expression coverage | ≥ 70% | ≥ 90% | ≥ 99% |
| FSM coverage | — | — | ≥ 99% |
| Functional coverage | ≥ 60% | ≥ 85% | ≥ 99% |
| Regression pass rate | ≥ 90% | ≥ 98% | 100% |
| All CHK_IDs passing | — | ✓ | ✓ |
| Zero unresolved gaps | — | — | ✓ |
Thresholds are overridable via coverage_config.yaml.
Print milestone table:
Milestone Closure Check
─────────────────────────────────────────────────────────────
Gate Status Blocking Metric
─────────────────────────────────────────────────────────────
DV-I ✓ PASS —
DV-C ✓ PASS —
DV-F ✗ FAIL Toggle coverage 90.8% < 95.0% required
FSM coverage 96.0% < 99.0% required
─────────────────────────────────────────────────────────────
Step 11 — Write dv_coverage_data.json
Assemble the complete coverage data JSON from all intermediate outputs.
python3 skills/common/scripts/generate_coverage_closure.py \
--mode write-data \
--project <project_name> \
--out dv/dv_coverage_data.json
Schema highlights:
{
"schema_version": "1.0",
"generated_at": "<ISO8601>",
"project_name": "<project>",
"tool": "urg",
"vdb_path": "<path>",
"code_coverage": {
"line": { "covered": 1240, "total": 1250, "pct": 99.2, "excluded": 5 },
"toggle": { "covered": 890, "total": 980, "pct": 90.8, "excluded": 20 },
"branch": { "covered": 430, "total": 440, "pct": 97.7, "excluded": 3 },
"expression": { "covered": 210, "total": 215, "pct": 97.7, "excluded": 2 },
"fsm": { "covered": 48, "total": 50, "pct": 96.0, "excluded": 1 },
"instances": [ ... ]
},
"functional_coverage": {
"total_bins": 40, "covered_bins": 33, "excluded_bins": 4, "pct": 82.5,
"covergroups": [ ... ]
},
"gaps_summary": {
"total_gaps": 23, "excludable": 14, "coverable": 7, "requires_analysis": 2,
"excluded": 14, "stubs_generated": 7, "skipped": 2, "pending": 0
},
"exclusions": { ... },
"stubs": { ... },
"milestone_results": { ... },
"sources": { ... }
}
Step 12 — Generate Sign-off HTML Report
Produce the combined sign-off report integrating S7, S9, and S10 data.
python3 skills/common/scripts/gen_coverage_signoff_report.py \
--coverage dv/dv_coverage_data.json \
--regression dv/sim/results/dv_regression_data.json \
--assertions dv/dv_assertions_data.json \
--milestone <output_dir>/milestone_results.json \
--project <project_name> \
--out <output_dir>/signoff_report/index.html
Report sections:
- Header + Sign-off Banner — GREEN/RED/YELLOW banner showing highest milestone achieved
- Milestone Gate Summary — 3-column table (DV-I / DV-C / DV-F) with PASS/FAIL per metric
- Coverage Dashboard — horizontal bars per metric with threshold markers
- Code Coverage Details — per-instance hierarchy with gap list
- Functional Coverage Details — per-covergroup/coverpoint/bin table
- Gap Analysis — full gap list with decisions and stub references
- Assertions (S7) — CHK_ID table with pass/fail status
- Regression Summary (S9) — pass/fail counts, top failures, pass rate
- Exclusion Review — all exclusions with justifications
- Recommended Actions — auto-generated action items to close remaining gaps
- Audit Trail — timestamps, urg version, VDB hash, git commit
The HTML is fully self-contained (no external dependencies) and can be emailed or checked in.
Step 13 — Terminal Summary
Print the final summary to stdout and write dv_coverage_closure_summary.txt.
╔═══════════════════════════════════════════════════════════════╗
║ S10 DV Coverage Closure — Summary ║
╠═══════════════════════════════════════════════════════════════╣
║ Project : apb_uart ║
║ Date : 2026-03-22 ║
╠═══════════════════════════════════════════════════════════════╣
║ Milestone Status ║
║ DV-I ✓ PASS ║
║ DV-C ✓ PASS ║
║ DV-F ✗ FAIL (2 metrics blocking) ║
╠═══════════════════════════════════════════════════════════════╣
║ Coverage (after exclusions) ║
║ Line: 99.2% Toggle: 90.8% Branch: 97.7% ║
║ Expression: 97.7% FSM: 96.0% Functional: 82.5% ║
╠═══════════════════════════════════════════════════════════════╣
║ Gaps: 14 excluded | 7 stubs generated | 2 skipped ║
╠═══════════════════════════════════════════════════════════════╣
║ Sign-off Report : sim/regression/signoff_report/index.html ║
║ Coverage Data : dv/dv_coverage_data.json ║
║ Exclusions : sim/regression/exclusions/combined.el ║
╠═══════════════════════════════════════════════════════════════╣
║ Next Actions ║
║ → Implement 7 test stubs in stubs/ ║
║ → Toggle coverage 90.8% needs +4.2% to reach DV-F ║
║ → FSM coverage 96.0% needs +3.0% to reach DV-F ║
╚═══════════════════════════════════════════════════════════════╝
Exit code: 0 if DV-F passes, 1 if DV-F fails (enables CI gating).
Directory Layout
dv/
├── dv_coverage_data.json ← main output
├── sim/
│ └── regression/
│ ├── merged.vdb ← input from S9
│ ├── urgReport/ ← text reports (generated by Step 2)
│ ├── urgReport_html/ ← HTML reports
│ ├── urgReport_excl/ ← post-exclusion text reports
│ ├── gaps/
│ │ ├── code_gaps.json
│ │ ├── func_gaps.json
│ │ ├── annotated_gaps.json
│ │ ├── classified_gaps.json
│ │ └── gap_decisions.json
│ ├── exclusions/
│ │ ├── line_exclusions.el
│ │ ├── toggle_exclusions.el
│ │ ├── branch_exclusions.el
│ │ ├── expression_exclusions.el
│ │ ├── fsm_exclusions.el
│ │ ├── functional_exclusions.el
│ │ └── combined.el
│ ├── coverage_after_exclusions.json
│ ├── milestone_results.json
│ ├── coverage_config.yaml
│ └── signoff_report/
│ └── index.html
└── sequences/ ← stubs placed alongside existing seqs
└── <protocol>/
└── *_coverage_seq.sv
Integration Notes
Makefile targets (added to dv/sim/Makefile by S9 but extended here)
coverage_closure:
python3 $(SCRIPTS)/generate_coverage_closure.py \
--project $(PROJECT) --vdb $(COV_DIR)/merged.vdb \
--reg-data $(COV_DIR)/dv_regression_data.json \
--assert-data dv/dv_assertions_data.json \
--out $(COV_DIR)
signoff_report:
python3 $(SCRIPTS)/gen_coverage_signoff_report.py \
--coverage dv/dv_coverage_data.json \
--regression $(COV_DIR)/dv_regression_data.json \
--assertions dv/dv_assertions_data.json \
--milestone $(COV_DIR)/milestone_results.json \
--project $(PROJECT) \
--out $(COV_DIR)/signoff_report/index.html
@echo "Sign-off report: $(COV_DIR)/signoff_report/index.html"
closure_full: cov_merge coverage_closure signoff_report
