Coverage Across Multiple Power Domains

What this topic teaches

Coverage Across Multiple Power Domains converts LPV concepts into staff-level verification decisions. Single-domain closure is insufficient once domains interact through shared clocks, buses, memory, and always-on control planes; coverage must capture cross-domain state combinations and transition interleavings that expose dependency bugs. Practical coverage models avoid combinational explosion by grouping states into risk classes (fully-on, retention, collapsed, transitional) and prioritizing high-impact intersections such as producer-off/consumer-on, shared-memory retention mismatches, and staggered wakeups across coherency participants. Each bin should tie to an observable correctness objective: no X-propagation into active logic, no stale data after restore, no orphaned transaction during domain collapse, and no interrupt loss across wake sequences. Signoff quality comes from merging simulation, emulation, and formal evidence into one closure view so unhit bins are triaged by silicon risk rather than waived on raw percentage pressure.

Senior-engineer framing question

When Risk-weighted coverage closure for domain-state cross products, inter-domain transition pairs, and wakeup cause by mode combinations. regresses, can you isolate first failing low-power boundary, prove it with artifacts, assign owners, and close with rollback-safe validation?

LOW-POWER VERIFICATION FLOW - Coverage Across Multiple Power Domains

power intent and mode definitions
      |
      v
domain controls and transition sequencing
      |
      v
simulation behavior (isolation, retention, corruption)
      |
      v
assertions and coverage evidence
      |
      v
triage, bounded fix, and signoff closure

Evidence to collect

• Primary metric: Risk-weighted coverage closure for domain-state cross products, inter-domain transition pairs, and wakeup cause by mode combinations..

• Primary artifact: Multi-domain coverage plan with cross-product reduction rules, risk-ranked bins, and signoff waiver criteria..

• Owners to include: verification lead, SoC low-power architect, emulation and prototyping owner, formal coverage owner, program quality owner.

• One reproducible failing scenario and one stable comparator run.

• One fixed metadata run with branch and configuration tags locked.

Ownership layers

OWNERSHIP LAYERS - Coverage Across Multiple Power Domains

+----------------------+--------------------------------+--------------------------------+
| Team                 | Primary responsibility         | Closure artifact               |
+----------------------+--------------------------------+--------------------------------+
| verification lead | scenario intent and closure      | review rationale memo          |
| SoC low-power architect | transition and boundary contract | timeline + assertion packet    |
| emulation and prototyping owner | regression signoff readiness     | validation matrix + risk note  |
+----------------------+--------------------------------+--------------------------------+

Decision matrix

EVIDENCE MATRIX - Coverage Across Multiple Power Domains

+-----------------------------+--------------------------------+--------------------------------+---------------------------+
| Evidence                    | Tells you                      | Does not prove                 | Next action               |
+-----------------------------+--------------------------------+--------------------------------+---------------------------+
| transition timeline traces  | first failing LP phase         | complete root-cause ownership  | correlate with intent map |
| UPF-aware assertion logs    | contract violations by phase   | silicon product impact         | map to scenario severity  |
| corruption/X classification | actionable vs noisy failures   | legal transition completeness  | replay key mode corners   |
| save/restore snapshots      | state integrity movement       | isolation correctness          | pair with crossing checks |
| before-after regressions    | mitigation movement quality    | long-tail stability            | run full matrix           |
+-----------------------------+--------------------------------+--------------------------------+---------------------------+

Key takeaways

• Start with transition-boundary classification before broad methodology changes.

• Tie each LPV claim to one proving artifact and one owner action.

• Close with validation matrix and rollback trigger for signoff safety.

Common pitfalls

• Waiving failures before first-failure boundary classification.

• Changing intent, RTL, and checkers in one step and losing causality.

• Declaring closure on local runs without broader replay coverage.

Low-power verification deep dive

Power-state correctness is a protocol contract: legal transitions, robust sequencing, and safe concurrent event handling.

Concept diagram

PST CONTROL LOOP

state request -> legality check -> handshake sequencing -> mode entry -> monitored exit

Metric graph

STATE RISK MIX

illegal transitions     ██████
sequence race bugs      █████
stable mode paths       ████████

Metrics and artifacts to collect

• PST legality matrix

• illegal transition histogram

• entry/exit handshake coverage

• mode sequencing anomaly log

Mini case study

A sporadic low-power failure closed only after proving a wake-versus-thermal race in PMU transition sequencing.

Debug branches

• Validate legal state graph first.

• Stress concurrent control events and asynchronous wakeups.

• Bind fixes to explicit transition and owner contracts.

Senior review question

Ask: what exact low-power transition boundary failed first, and which artifact proves the closure claim reproducibly?

Key takeaways

• Tie each LPV claim to a concrete transition boundary and one proving artifact.

• Prefer minimal reversible fixes with explicit owner and rollback criteria.

Common pitfalls

• Treating power-aware failures as random before boundary classification.

• Waiving X-prop failures before proving impact and root cause.

• Declaring closure without deterministic replay across key modes.