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powerd620-nvpcf-trace.md

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NVPCF route trace for the 620 nvidia-powerd

scripts/powerd620-nvpcf-branch.bt records which NVPCF route the unmodified nvidia-powerd takes at start. It does not change the GPU clock. Its 11 probes only read registers and memory, for the bpftrace child only. The traced nvidia-powerd makes its normal vendor calls, which can set platform values. The trace forces and overrides nothing. The offsets fit only the 620.70.06 binary below.

Run

Boot the @nv620 root with bpftrace 0.27.0 and no nvidia-powerd process. Set REPO to this repository and RUNS to an existing private directory. Start the trace once. Each start writes to a new directory under RUNS.

(
  set -eu; umask 077
  B=$(realpath -e "${REPO:?set REPO}/scripts/powerd620-nvpcf-branch.bt"); [ -f "$B" ]   # absolute before cd
  [ "$(findmnt -no FSROOT /)" = /@nv620 ]
  echo 'eb9e0371f73667f242e8d4742e17a21a68470e08cdc6438a84c263a4c3b6f4d2  /usr/bin/nvidia-powerd' | sha256sum -c --quiet
  [ "$(pgrep -xc nvidia-powerd)" = 0 ]
  R=$(mktemp -d "${RUNS:?set RUNS}/powerd620-trace-XXXXXX"); cd "$R"; echo "run directory: $R"
  set +e
  sudo -n timeout -k 5 60 bpftrace -k -v -q -o T-trace.txt -c /usr/bin/nvidia-powerd "$B" 2> T-stderr.txt
  rc=$?; echo "rc=$rc" > T-rc.txt
  { pgrep -xc nvidia-powerd; pgrep -xc bpftrace; } > T-after.txt
  exit "$rc"
)

If a setup check fails, the subshell stops before it makes the run directory or starts the trace. The trace exit code and stderr are kept when they are nonzero, and the subshell exits with the trace exit code.

-k reports probe-read errors, which bpftrace hides by default. -v logs Child exited with code: N or Child terminated by signal: N. At 60 s, bpftrace gets TERM, runs END and kills the child. If T-after.txt is not two zeros, record the remaining PID and stop.

Read the result

Report the raw lines, then apply these rules in order.

  1. VALID only if T-rc.txt is rc=0, stderr has Child exited with code: 0, the trace has BEGIN, END and factory_create_entry, and stderr has no Failed to probe_read, lost-event, attach or parse error. Otherwise INCONCLUSIVE. A timeout (124), a kill (137) or a signal-stopped child is never a normal exit.
  2. Route (a), 3x init: nvpcf3x_init_ret bool=1, factory_3x_true_branch, main_no_worker. Report nvpcf3x_objprim_ptr with it: 0 means the wrapper skipped its call, nonzero means only that the call path was taken. Neither shows a running controller.
  3. Route (b), fallback to 2x/1x: nvpcf3x_init_ret bool=0, factory_3x_false_branch, nvpcf2x_ret (raw).
  4. Anything else: INCONCLUSIVE, with the events listed.

Report nvpcf3x_query_raw for both routes. It does not decide the route. has_value=0 means the query failed with the status in the low 32 bits (0x56 is not supported). has_value=1 means only that the query succeeded. quit_entry w0=0x2 decides nothing, because 2 is also SIGINT. Report factory_mobile_clear if it occurs.