Save/Restore Handshake Sequencing: Design Space

Design space exploration

For Save/Restore Handshake Sequencing, teams balance safety, closure speed, and simulation or debug cost.

Option A - conservative

• Conservative controls: helps strong safety and clarity

• Risk: higher setup and runtime overhead

• Validate with: new LPV program bring-up

Option B - balanced

• Balanced controls: helps good closure velocity

• Risk: needs disciplined review

• Validate with: shared platform verification

Option C - aggressive

• Aggressive optimization: helps lower overhead

• Risk: higher corner-case risk

• Validate with: mature flows with strong telemetry

Option D - refactor

• Refactor path: helps long-term robustness

• Risk: migration cost

• Validate with: legacy LPV debt cleanup

DESIGN SPACE - Save/Restore Handshake Sequencing
coverage depth <-> simulation/runtime cost <-> debug clarity <-> residual risk

Design pitfalls

• Optimizing runtime before proving intent-correctness boundaries.

• Adding checks without ownership of closure and triage workflow.

Low-power verification deep dive

Retention closure requires proving end-to-end state lifecycle through save, off, and restore windows.

Concept diagram

RETENTION LIFECYCLE

save request -> state capture -> power off -> power on -> restore -> traffic resume

Metric graph

RETENTION STABILITY

restore mismatch       █████
save timing defects    ████
stable wake cycles     ███████

Metrics and artifacts to collect

• retention save/restore timing report

• pre/post state diff matrix

• multi-cycle retention stress summary

• state-loss bug trend by mode

Mini case study

A corruption issue persisted until retention checks compared multi-cycle state snapshots rather than single wake events.

Debug branches

• Track save acknowledgement against actual state capture.

• Validate restore completion before functional traffic resumes.

• Run repeated sleep/wake cycles to expose drift.

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.

Principal LPV review addendum

Save/Restore Handshake Sequencing should be reviewed as a transition integrity system, not just isolated checks.

Use Handshake protocol compliance rate, save-to-off and restore-to-functional timing margin, and timeout escape count. as alarm and Temporal handshake checker suite with protocol assertions, timeout diagnostics, and scenario-wise latency histograms. as proof.

Retention closure requires proving save, off, and restore phases as one lifecycle with explicit handshake timing. Closure quality comes from reproducible evidence and explicit owners.