22 lines
1.5 KiB
Markdown
22 lines
1.5 KiB
Markdown
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# Intel X710 (i40e)
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## Module I2C: 1-byte-offset only — dead end for BCM SMI
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- `reg_address > 0xFF` returns AQ retval 14 (hard boundary).
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- Emits at most `[dev, offset, data]` (2 payload bytes); the BCM SMI needs 3–5 byte frames in one transaction.
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- MDIO interface modes don't reach the module — no PHY on the NIC MDIO pins; copper SFPs wire only I2C.
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- Single-byte **writes work** (unlike the E810) — which is what makes the oracle path below possible.
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## AQ oracle path (stock driver) — proved the RollBall client logic
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- Transport: `/sys/kernel/debug/i40e/<pci>/command`, `send aq_cmd <flags> <opcode> 0 0 0 0 <param0> <param1> <param2> 0`, flags 0x2000.
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- Opcode 0x0629 get / 0x0628 set PHY register. param0 = phy_interface | dev_addr<<8 | cmd_flags<<16 (phy_interface 2 = EXTERNAL_MODULE, dev_addr 0xA2); param1 = reg offset; param2 = value.
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- Result comes back in the dmesg "AQ desc WB" line, 9th field.
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- Proven on the Fibergaga, link up: per-pair SNR (PMA 1.133–1.136), PCS 3.32/3.33, the 3.E820 counter ([../../modules/fibergaga/](../../modules/fibergaga/README.md)).
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## Timestamping
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- Rejects `HWTSTAMP_FILTER_ALL` with -ERANGE (verified in upstream `i40e_ptp.c`) — PTP-only, so no committed-path bucketing here.
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- Genuinely shared PHC across ports (one oscillator) + PTP latches: the platform for the retrain-stability experiment and the scoped-but-unbuilt PTP path-delay length fallback ([../../open-questions.md](../../open-questions.md) §2) — probes must be PTP-shaped here too.
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- No EEE on i40e/X710.
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