Re: [RFC PATCH] thunderbolt: Tunnel only the first DP OUT of Apple Studio Displays

["Duff O'Melia" <duff@omelia.org>]

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Hi Mika,

On Mon, Nov 09, 2026 at 11:30:39AM +0100, Mika Westerberg wrote:
> Can you provide full dmesg with thunderbolt.dyndbg=+p and drm.debug=0x10e
> in the kernel command line when you have everything connected and the issue
> reproduces?

Sure, it's attached, xz-compressed. It's from a reboot with everything
connected, on Omarchy's 7.2.15 kernel with its stock Thunderbolt driver
(my patch not applied). I added log_buf_len=64M so the start of the boot
isn't lost. I removed MAC addresses, USB serial numbers and some
firewall log lines, and changed nothing else.

In short:

- 0-3 is the 2026 model (0x8025). Both of its DP OUT adapters got
  tunneled: 0:5 <-> 3:11 and 0:10 <-> 3:12.
- 1-1 is a 2022 model (0x801f) on the second host router. It got
  0:6 <-> 1:10.
- 0-1 is the other 2022 model. It came up last, found no free DP IN
  adapter ("no suitable DP IN adapter available, not tunneling") and
  stays dark.
- In xe, DP-1 (DPTUN 0:1:5) is the 2026 model's first tile, DP-3
  (DPTUN 0:1:10) its second tile, and DP-2 (DPTUN 1:1:6) the 2022
  model. DP-1 and DP-2 run at 5120x2880.

One correction to my patch description: on this boot DP-3 isn't
disabled. Pipe D is active on it at 2560x2880 with no framebuffer on its
primary plane, and the compositor doesn't list it as a monitor. So the
second tile's stream does come up, but it shows nothing.

I'm happy to run anything else, such as the same boot with the patch
applied for comparison.

Thanks,
Duff


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