[Bug 2143197] Re: UBUNTU: SAUCE: igc: Increase Thunderbolt MAC passthrough delay to 1000ms

** Tags removed: verification-needed-noble-linux-oem-6.17
** Tags added: verification-done-noble-linux-oem-6.17

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https://bugs.launchpad.net/bugs/2143197

Title:
UBUNTU: SAUCE: igc: Increase Thunderbolt MAC passthrough delay to
1000ms

Status in linux package in Ubuntu:
Fix Released
Status in linux-oem-6.17 package in Ubuntu:
Invalid
Status in linux source package in Noble:
Invalid
Status in linux-oem-6.17 source package in Noble:
Fix Committed
Status in linux source package in Resolute:
Fix Released
Status in linux-oem-6.17 source package in Resolute:
Invalid

Bug description:
BugLink: https://bugs.launchpad.net/bugs/2143197

[Impact]
Dell Thunderbolt dock ethernet (Intel I226 NIC) can fail to initialize after
hotplug with MAC passthrough enabled. After unplug/replug, the interface may appear with an dock MAC address but not MAC passthrough address then cause stale MAC and wired networking does not work.
Cold boot is unaffected; issue is hotplug-specific.

Affected systems include Dell platforms with Thunderbolt docks such as
SD25TB5-class docks carrying Intel I226 ethernet.

[Fix]
Increase the existing Thunderbolt MAC passthrough wait in igc probe path:
- from 600ms
- to 1000ms

Ubuntu already carries a SAUCE workaround (commit 534981aaa831) that uses
fixed delay timing. Newer Dell docks need a longer timing window.

Debug testing shows BIOS MAC update timing:
- cold boot: MAC already correct at probe start
- hotplug: MAC becomes correct at ~300-800ms after probe starts

Use 1000ms (observed 800ms worst-case + margin) to make hotplug
reliable.

Upstream context:
https://lore.kernel.org/lkml/20210702045120.22855-2-aaron.ma@canonical.com/
(Upstream preferred polling over fixed delay; Ubuntu keeps minimal stable
fixed-delay workaround.)

[Test Plan]
1. Boot with dock attached; confirm interface has valid MAC and link works.
2. Unplug dock, wait 5s, replug, wait for enumeration.
3. Verify MAC is valid/correct and connectivity works.
4. Repeat hotplug cycle 10 times.

Expected results:
- Without this change: intermittent hotplug failures (~50-80% observed).
- With this change: MAC is correct and networking works on every cycle.

[Where problems could occur]
- Probe time for Thunderbolt-attached igc devices increases by 400ms.
- Scope is limited to pci_is_thunderbolt_attached() path.
- If a future dock requires >1000ms, hotplug failure could still occur.
- No functional changes beyond extending an existing sleep.

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