Resolve X520 open questions on hardware: ETQF raw-L2 steering and single-hold compound I2C proven; 82599 has no all-packet exact-timestamp path so it is disqualified as product NIC (diagnostics-only), counter route rejected for a cable tester

2026-08-12 20:36:31 -07:00
parent 910379e614
commit 5588ebec6f
5 changed files with 50 additions and 43 deletions
@@ -12,7 +12,7 @@ Dual SFP28, PCIe x8. mlx5 is the one driver meeting the full requirement set:
 - Whether firmware MCIA accepts **arbitrary I2C device addresses** — the BCM bridge sits at 0x56; kernel paths only ever use 0x50/0x51.
 - Whether the BCM SMI **read data phase** (raw 2-byte read, no offset write) can be framed through MCIA's offset model.
 - RollBall (0x51-resident, offset-model) fits MCIA — low risk.
- If MCIA can't reach the BCM: product diagnostics via the Marvell/Aquantia modules only, X520 kept as an offline BCM rig — or the X520 as fallback product NIC if the bucket exploration validates ([../../open-questions.md](../../open-questions.md) §2, §6).
+- If MCIA can't reach the BCM: product diagnostics via the Marvell/Aquantia modules only, X520 kept as an offline BCM rig. The X520 is **not** a fallback product NIC — it has no all-packet exact-timestamp path, which a cable tester's rate buckets require ([../../open-questions.md](../../open-questions.md) §2, §6).

 ## Arrival notes