[Ante042]

Hi! These three come from running two USB-C displays and a USB-C dock on an M1 Pro (J314s) with the Omarchy kernel. Outside compositor pairing order, a port in DP alt mode takes a pipeline as soon as it enters DP mode, even when nothing behind it asserts HPD. A dock without a display does exactly that, and with two pipelines one of the displays stays dark. It also happens at boot, when the PD controllers report a DP state for ports with nothing behind them, which is how the LUKS prompt ends up on the internal panel of a closed laptop (omarchy-pkgs#1037).

The first patch lets a port with HPD take over a pipeline held by a port that never asserted it. The second keeps such a port unrouted until its sink asserts HPD, so the takeover is only left for corner cases. Once, a hand-over right after the dock had been routed left the DPTX service on that DCP answering -110 until reboot. The third is in tipd: the fabric now reports a port without a pipeline as -ENOSPC on every SoC, but cd321x_display_taken() only accepts that on H17. On t600x the dock's DP setup failed with -28 three times, the cable revalidation failed and nothing behind the dock came up.

I've been running the takeover and the tipd change on 7.2.10 since the 20th and the second patch since the 22nd. The setup is a ROG and a VG278 on two ports and the dock on the third. Both displays come up at boot and after replugs, the dock never gets a pipeline, and its USB works. The patches are rebased onto 42672ed and build against 7.2.11. Happy to test anything else on the J314s. This replaces aurora-silicon/linux#302.

[greptile-apps]

Confidence Score: 5/5

[Medium impact] The PR appears safe to merge.

Summary

Keeps direct DP-alt ports without HPD from taking a display pipeline.

• Ports without HPD leave display pipelines free for connected displays.
• The Type-C controller treats -ENOSPC as a taken display on every SoC.

No actionable issues were found.

Diagram

%%{init: {'theme': 'neutral'}}%%
flowchart TD
  A[Direct DP-alt update] --> B{Port owns a pipeline?}
  B -->|No| C{HPD high?}
  C -->|No| D[Remember state without routing]
  C -->|Yes| E{Free pipeline?}
  E -->|Yes| F[Activate route]
  E -->|No| G{Eligible HPD-low owner?}
  G -->|Yes| H[Release old route]
  H --> F
  G -->|No| I[Return ENOSPC; USB setup continues]
  B -->|Yes| J[Update existing route]

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_{Reviews (1) · Last reviewed commit: "usb: typec: tipd: treat -ENOSPC as a tak..." · Reviewed by Greptile}

[invaliddayta]

The third commit here (2a37f6f206, tipd) fixes the same bug as #163, which I opened on 10-20 for a MacBook Air M2 (J413, T8112). There, a USB-C monitor in one port leaves a DP Alt Mode dock in the other without USB (failed to configure Type-C connection: -28, then cable revalidation failed after 3 attempts).

The two differ in one point:

• usb: typec: tipd: keep a dock's USB when the display pipeline is taken #163: cd321x_display_taken() is ret == -ENOSPC on every SoC, so an -EBUSY (for example from the ATC PHY during a transition) is retried everywhere.
• Here: -EBUSY still counts as a taken display outside H17. That is the narrower alternative usb: typec: tipd: keep a dock's USB when the display pipeline is taken #163 lists.

From the code, both fix the T8112 case, because the fabric reports -ENOSPC there. I have only tested the #163 version: on 7.2.10, 10 of 10 -28 events got the dock's USB back within 3 s, against 0 of 3 plugs without the patch.

Only one of the two should be merged. If this one goes in, #163 can be closed.