RISC-V Design · All levels

Trace and Debug Modules: Debug Playbook

Debug Playbook for Trace and Debug Modules.

Debug playbook

Debug Playbook for Trace and Debug Modules is anchored on Average time-to-root-cause for failing regressions using trace capture and debug trigger workflows.. Convert observations into mechanism-backed decisions with explicit ownership.

Freeze workload seed, binary, compiler, firmware, and platform setup.
Find earliest persistent mechanism failure in the timeline.
Build one reduced reproducer for dominant hypothesis.
Patch minimal fix with explicit rollback gate.
Rerun correctness + performance + power matrix.

Decision tree

diagram

ROOT CAUSE TREE - Trace and Debug Modules

Average time-to-root-cause for failing regressions using trace capture and debug trigger workflows. regressed
          |
   reproducible on fixed seed?
      /                 \
    no                   yes
    |                     |
env/tool drift       first failing domain?
                     /        |         \
                  decode    execute    memory/MMU
                    |         |            |
               control map  bypass/FU   TLB/walk/perm
                    |
         privilege/CSR side effects checked?

Stop at first confirmed mechanism, then assign explicit owner + fix proof.

Review memo template

diagram

RISC-V REVIEW MEMO - Verification & Debug / Trace and Debug Modules

1. Symptom
   - Failing metric: Average time-to-root-cause for failing regressions using trace capture and debug trigger workflows.
   - Failing workload slice: <name>
   - Triggering mode: <privilege/virtualization/interrupt/cache/boot>
   - Build and runtime tags: <toolchain/firmware/RTL revision>

2. Mechanism hypothesis
   - Primary mechanism: RISC-V debug effectiveness depends on observability through trace streams, trigger units, and standard debug module access to core state. Instruction/data trace, retired-PC history, and selective event triggers let engineers reconstruct causal execution around rare failures without rerunning full-wave dumps every time. Well-structured debug integration defines which signals are always visible, which are sampled on trigger, and how software tooling correlates hardware traces with ELF symbols and disassembly for fast issue localization.
   - Competing hypotheses: <decode control / hazard / MMU / privilege / integration>
   - Missing evidence: <trace/counter/proof/report>

3. Proposed action
   - Smallest reversible change: <RTL/compiler/runtime/config>
   - Expected movement: <throughput/latency/tail/perf-per-watt>
   - Regression risk: correctness, security, power, timing, software compatibility

4. Signoff
   - Required artifact: Debug observability plan with trigger cookbook, trace retention policy, and toolchain correlation flow.
   - Required owners: CPU verification lead, debug architecture owner, firmware validation owner, post-silicon lead
   - Final decision: ship, bounded rollout, rollback, or escalate

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