Strip canaries, double-reads, retries and floors from the module protocol; every bcm method holds the per-module lock for its whole operation; facts stay in docs with internal-client contention marked unresolved
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@@ -23,9 +23,9 @@ Protocol and full verified catalog: [bcm84891l-mdio-commands.md](bcm84891l-mdio-
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- **SET commands execute stale DATA** — the handler never clears DATA registers; write every parameter register explicitly before any SET.
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- **GETs must be invoked bare** — pre-writing *any* DATA register, not just the documented DATA1 display flag, leaves the handler executing as a no-op with results never written (sentinel pre-fills survived GET_SNR untouched, proven on hardware).
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- **STATUS must never be written** — any user value (0x0000 and 0x0008 both tried) closes the mailbox: the next command is silently ignored until firmware restores it.
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- **PASS cannot prove completion.** The previous command's PASS stays latched while a slow firmware still executes, and until then the DATA registers are firmware scratch — the die temperature turns up in them (0x004E–0x0051 observed as "SNR" and "EEE mode"; the campaign's "anomalous 0x0047" was this same race). cabletest reads results twice and requires agreement (DATA1 excluded — temperature lands there autonomously), and discards SNR samples below 15 dB absolute, far under anything a trained link produces and exactly where every garbage signature sits.
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- **PASS cannot prove completion.** The previous command's PASS stays latched while a slow firmware still executes, and until then the DATA registers are firmware scratch — the die temperature turns up in them (0x004E–0x0051 observed as "SNR" and "EEE mode"; the campaign's "anomalous 0x0047" was this same race).
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- **Handler writes during firmware-busy windows wedge the µC permanently** — DATA/CMD writes landing while firmware does post-AN provisioning or training work (a window stretching ~10 s past relink) killed the SMI service four times; reads alone never once. Every handler write — SETs, GET commands, the ECD trigger — runs only in a quiet window: carrier up and stable ≥ 10 s (`phy.go`).
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- **Bridge reads carry no fetch identity** — a fetch that outruns the delay leaves the previous transaction's data at 0xAD with no error. cabletest brackets read batches with a known-answer canary (PHY ID 1.2 = 0x3590) and discards the batch on mismatch (`phy.go`).
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- **Bridge reads carry no fetch identity** — a fetch that outruns the delay leaves the previous transaction's data at 0xAD with no error.
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- Poll STATUS ~100 ms; frozen up to 2 s during 10GBASE-T training — only run after link-up.
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## Proven diagnostics
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@@ -54,7 +54,7 @@ Protocol and full verified catalog: [bcm84891l-mdio-commands.md](bcm84891l-mdio-
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## Firmware-reliability notes
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**The firmware is its own mailbox client — the handler is a shared, unarbitrated resource.** Watched read-only on an idle module: CMD sits at 0x0031 (`CMD_GET_CURRENT_TEMP`, bit 15 consumed) and DATA1 tracks the live die temperature (0x4F–0x52 ≈ 79–82 °C under load), refreshed every ~3.5 s — the firmware issues its own temperature command through the same CMD/STATUS/DATA registers the host uses, with no arbitration. Every mystery this explains: temperature appearing in DATA1 (it is that command's output — the campaign's "anomalous 0x0047" included), PASS satisfying a host poll when it belongs to the internal command, and the µC wedges (two writers colliding on CMD/DATA, likeliest when internal management activity spikes after AN events). Host defenses in `phy.go`: quiet-window writes, double-read results (DATA1 excluded), a CMD readback proving the command was not interleaved, the PHY-ID canary, and the SNR floor. Any GET whose answer lives in DATA1 is unusable; corroborate through IEEE registers or the wire. The hard rule that stands: write every DATA register explicitly before any SET — the handler executes stale DATA.
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**The firmware is its own mailbox client — the handler is a shared, unarbitrated resource.** Watched read-only on an idle module: CMD sits at 0x0031 (`CMD_GET_CURRENT_TEMP`, bit 15 consumed) and DATA1 tracks the live die temperature (0x4F–0x52 ≈ 79–82 °C under load), refreshed every ~3.5 s — the firmware issues its own temperature command through the same CMD/STATUS/DATA registers the host uses, with no arbitration. Every mystery this explains: temperature appearing in DATA1 (it is that command's output — the campaign's "anomalous 0x0047" included), PASS satisfying a host poll when it belongs to the internal command, and the µC wedges (two writers colliding on CMD/DATA, likeliest when internal management activity spikes after AN events). The host side keeps exactly one conversation open at a time (one per-module lock around every whole operation, `phy.go`) and confines writes to quiet windows; **contention with the internal client is otherwise unresolved** — a host GET can still be preempted (~10% per command at the temp cadence) and its results replaced. Any GET whose answer lives in DATA1 is unusable; corroborate through IEEE registers or the wire. The hard rule that stands: write every DATA register explicitly before any SET — the handler executes stale DATA.
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## ECD — recovered from the OpenBCM SDK, proven on hardware
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+1
-1
@@ -2,7 +2,7 @@
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## Committed tree
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AF_PACKET raw sockets everywhere (`sock.go`); flow-director steering; per-packet-MAC-rx-stamped rate buckets (`SO_TIMESTAMPING` cmsg, `rx_filter=ALL` as a hard host check — nics/README.md for what that demands of the NIC; **temporarily bypassed** in `ts.go` so BCM work can run on the X520, which cannot stamp — the check reports yellow and the panel rates read zero there; restore to fatal for the product NIC); read-time-stamped NIC-counter rates; test interfaces pinned to MTU 9000 with a 9018-byte jumbo in the size mix (the modules' jumbo path is exercised, not assumed); BCM module diagnostics (`phy.go`, over the patched-ixgbe `sff_i2c` debugfs, compound-op framing; handler writes confined to quiet windows — the µC wedges otherwise — with results double-read, canary-validated, and floor-checked — modules/fs/ for the full trap list): bringup identifies both modules and forces EEE off and jumbo on every boot — no trustworthy readback exists and no cable is guaranteed to probe through; the ECD — per-pair verdicts, lengths and pair maps are the length/wiring path — runs through one async path at startup and on every reset, never blocking the UI, with counters re-baselining only after the diag's own link blip so it is never charged to the run; a 1 Hz poller feeds per-pair SNR margin (vs the ≈26.5 dB operating point; green ≥ 3 dB, amber ≥ 1 dB — provisional until the graded-noise run) and the corrected-error set (PCS 3.33 errored blocks/BER, PMA 1.147 fast-retrain count) to the panel and console; framebuffer UI; harness.
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AF_PACKET raw sockets everywhere (`sock.go`); flow-director steering; per-packet-MAC-rx-stamped rate buckets (`SO_TIMESTAMPING` cmsg, `rx_filter=ALL` as a hard host check — nics/README.md for what that demands of the NIC; **temporarily bypassed** in `ts.go` so BCM work can run on the X520, which cannot stamp — the check reports yellow and the panel rates read zero there; restore to fatal for the product NIC); read-time-stamped NIC-counter rates; test interfaces pinned to MTU 9000 with a 9018-byte jumbo in the size mix (the modules' jumbo path is exercised, not assumed); BCM module diagnostics (`phy.go`, over the patched-ixgbe `sff_i2c` debugfs, compound-op framing; one per-module lock around every whole operation, handler writes confined to quiet windows — the µC wedges otherwise; the firmware's own mailbox use still contends, unresolved — modules/fs/ for the full trap list): bringup identifies both modules and forces EEE off and jumbo on every boot — no trustworthy readback exists and no cable is guaranteed to probe through; the ECD — per-pair verdicts, lengths and pair maps are the length/wiring path — runs through one async path at startup and on every reset, never blocking the UI, with counters re-baselining only after the diag's own link blip so it is never charged to the run; a 1 Hz poller feeds per-pair SNR margin (vs the ≈26.5 dB operating point; green ≥ 3 dB, amber ≥ 1 dB — provisional until the graded-noise run) and the corrected-error set (PCS 3.33 errored blocks/BER, PMA 1.147 fast-retrain count) to the panel and console; framebuffer UI; harness.
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## Stashes
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