# Spike: Evaluate SSP 2.7.0 USBX modernization and Renesas HCD interoperability

Status: complete
Result: complete; documented/no action
Type: spike
Updated: 2026-08-14
Next Action: none; retain as research history and reopen only on explicit owner authorization with new contradictory evidence
Campaign: 003-complete-bounded-hpt-slow-export-firmware-ticket
Parent: work/maps/map-smi-firmware-stabilization-and-qualification.md
Disposition: no-action
Produces:

## Final Disposition

The owner does not have an inline analyzer and directed this investigation to
stop. T00 remains unresolved no-action architecture evidence and does not
authorize analyzer acquisition, SSP migration, HCD patching, Controller B
changes, or Renesas escalation. This spike may be reopened only by explicit
owner authorization based on new contradictory evidence.

## Question

Would an isolated SSP 2.7.0 migration materially improve USB mass-storage
compatibility and lifecycle correctness without unacceptable regression risk,
and does the S7G2 `sf_el_ux` host controller exhibit Renesas issue 13481
(unexpected PING after ACK) on this hardware?

## Timebox

Planning and read-only comparison first: at most two focused sessions. A
protocol-analyzer capture, sandbox migration, generated-code change, build,
deployment, or hardware run requires separate authorization.

## Findings

- Current project: SSP 2.6.1 with USBX/FileX 6.2.1.
- Current public Renesas release: SSP 2.7.0 with USBX/FileX 6.4.0.
- Renesas still lists HCD issue 13481 in SSP 2.7.0: USB host PING may be sent
  after ACK, contrary to expected USB 2.0 behavior; no workaround is published.
- Middleware modernization cannot substitute for the R5 teardown and
  fresh-session contract.
- Editing generated/vendor SSP source is not an acceptable durable solution.
- The official SSP 2.7.0 release note reviewed on 2026-08-01 still lists issue
  13481 without a workaround, while confirming USBX 6.4.0 integration. The
  newly captured T00 failure is a pending Bulk-IN CSW request with no HCD
  completion/error indication at abort entry. That is compatible with, but
  does not prove, issue 13481.

## Recommendation

Keep this spike behind the R5 lifecycle gate. Use a USB protocol analyzer
before proposing a user-owned HCD patch: capture the last successful and
failing Bulk-IN CSW phases, including token/PING and device handshake/data
responses, and correlate them to the exact-abort telemetry. Request a Renesas
disposition only with that trace. If migration is recommended, create a
separate workpackage and qualify it independently from write-size and
lifecycle changes.

No USB protocol analyzer is currently available, so this spike cannot prove or
dismiss issue 13481 on the target. Do not treat a migration as a substitute for
the missing trace.

## Follow-Up

- Historical planning item: Produce a source-level 6.2.1-to-6.4.0 storage lifecycle/BOT delta.
- Historical planning item: Inventory SSP 2.7.0 regeneration and integration risk for this dirty tree.
- Historical planning item: Obtain Renesas support disposition for issue 13481.
- Historical planning item: Define the minimum analyzer capture needed to confirm or dismiss the PING
  behavior on S7G2.
- Historical planning item: Recommend migrate, targeted backport, HCD patch, or no action.

When the spike finishes, set `Disposition:` to `planned`, `documented`, `no-action`, or
`superseded`. A `planned` disposition must name the follow-up `work/*.md` artifact in `Produces:`.
