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CPU/AP blocker status

packages/chip/docs/project/cpu-ap-blocker-status-2026-05-17.md

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CPU/AP blocker status

Date: 2026-05-17

Scope: rtl/cpu/**, CPU-facing contract tests, and project CPU/AP status.

Current Local Artifact

The only in-repo executable CPU artifact is rtl/cpu/e1_cpu_subsystem_stub.sv. Despite the legacy module name, it is a tiny hand-written RV-style contract CPU, not a Linux-capable application processor.

Locally proven by make cocotb-cpu:

  • reset identity is exposed as RESET_PC=0x8000_0000 and HART_ID=0 in the CPU contract wrapper,
  • fetch starts at the reset boundary,
  • the tiny CPU executes the documented small integer/load/store/control-flow subset,
  • unsupported, privileged, CSR, unaligned, and bus-error paths halt fail-closed,
  • timer, software, and external interrupt inputs are pending-level placeholders only.

Not proven:

  • RV64GC compliance,
  • CSR/trap behavior,
  • M/S/U privilege modes,
  • interrupt or exception entry/return,
  • CLINT/ACLINT timer/software interrupt compatibility,
  • PLIC/IMSIC compatibility beyond the local claim/complete scaffold,
  • MMU, page-table walks, caches, atomics, compressed instructions, floating point, or coherent memory,
  • boot ROM execution, OpenSBI handoff, Linux boot, Android boot, UART console, or generated DTS consistency.

The single Rocket RV64GC hart is not a 2028 phone-class AP. It is acceptable as the first Linux bring-up target only. A phone-class claim remains blocked on a selected multi-hart or documented-equivalent CPU topology, ISA compliance, cache/coherency/MMU evidence, sustained benchmark data, power/thermal measurement, Android userspace evidence, and silicon/board evidence.

Selected Open CPU/AP Path

The selected path is a generated Chipyard Rocket RV64GC subsystem. The selection is pinned in generators/chipyard/eliza-rocket-manifest.json:

  • Chipyard 1.13.0, commit 69eba860a352343e4ac6b6df0f3638a79a86ec78,
  • single Rocket RV64GC hart for first AP integration,
  • project config name ElizaRocketConfig,
  • production wrapper name eliza_rocket_ap,
  • generated import manifest expected at build/chipyard/eliza_rocket/ElizaRocketConfig.manifest.json.

No generated Chipyard/Rocket RTL, simulator, DTS, firmware image, or boot log is present in this repository yet. Therefore the CPU/AP path is blocked on external generator integration, not on more hand-written tiny-CPU expansion.

Host Checks

  • make chipyard-generator-check verifies the selected AP path is pinned and non-claiming.
  • make chipyard-generated-check is expected to fail until generated artifacts exist, the generated import manifest records recursive submodules, commands, tool versions, artifact paths, and SHA-256 values, and those paths validate against docs/evidence/cpu-ap-evidence-manifest.json.
  • make cpu-ap-evidence-check is expected to fail until real OpenSBI/Linux and trap/timer/IRQ/cache/MMU/benchmark evidence logs exist. Archive real external transcripts with python3 scripts/capture_cpu_ap_evidence.py intake ...; the helper only accepts logs containing the manifest-required AP boot/trap/cache and benchmark markers.
  • make cpu-ap-completion-gate stays blocked until the selected manifest makes a real AP claim and the generated artifacts plus transcripts validate.
  • sw/platform/e1_platform_contract.json must remain has_cpu=false until generated CPU/AP artifacts and boot evidence exist.

Current missing evidence paths:

  • build/evidence/cpu_ap/eliza_e1_opensbi_boot.log
  • build/evidence/cpu_ap/eliza_e1_linux_boot.log
  • build/evidence/cpu_ap/eliza_e1_trap_timer_irq.log
  • build/evidence/cpu_ap/eliza_e1_isa_cache_mmu.log
  • build/evidence/cpu_ap/eliza_e1_ap_benchmarks.log

Next CPU/AP commands:

sh
make chipyard-generator-check cpu-ap-scaffold-check cpu-ap-completion-gate
python3 scripts/check_chipyard_import_preflight.py --require-checkout
make chipyard-generated-check cpu-ap-evidence-check cpu-ap-completion-gate

CPU/AP Blocker Status

The current checked-in CPU path is a tiny executable scaffold for contract tests. It is not a Linux-capable application processor and must not be used as phone CPU evidence.

Current Gate

  • The platform contract remains has_cpu=false until a production CPU is integrated at the package top.
  • No generated Chipyard/Rocket RTL is checked in for the product CPU/AP path.
  • OpenSBI plus Linux early console evidence is missing.

Required Evidence

Before any Linux-capable CPU claim is unblocked, the repo needs checked transcripts for OpenSBI, Linux early console, trap and interrupt behavior, mcause, mepc, mtimecmp, external interrupt claim/complete, and firmware-to-kernel handoff.