linux-kernel - Re: [PATCH] [RFC] thunderbolt: Add delay for Dell U2725QE link width

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Message-ID: <20251218102021.GV2275908@black.igk.intel.com>
Date: Thu, 18 Dec 2025 11:20:21 +0100
From: Mika Westerberg <mika.westerberg@...ux.intel.com>
To: "Chia-Lin Kao (AceLan)" <acelan.kao@...onical.com>,
	Mario Limonciello <mario.limonciello@....com>,
	Andreas Noever <andreas.noever@...il.com>,
	Mika Westerberg <westeri@...nel.org>,
	Yehezkel Bernat <YehezkelShB@...il.com>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, Sanath.S@....com,
	"Lin, Wayne" <Wayne.Lin@....com>
Subject: Re: [PATCH] [RFC] thunderbolt: Add delay for Dell U2725QE link width

On Thu, Dec 18, 2025 at 03:35:05PM +0800, Chia-Lin Kao (AceLan) wrote:
> > Now since USB 2.x has its own wires in Type-C cable this tells me that
> > there is some real problem with the connection. Have you tried different
> > cables already?
> Here is the log I got with another tbt4 cable.
> I'm using the kernel with Mario suggests modification.
> 
> https://people.canonical.com/~acelan/bugs/tbt_call_trace/intel/merged_6.18.0-d358e5254674+.patched2.2_new_cable.out

Here I see (assuming I read it right) that the USB 2.x enumerates only
after the first unplug:

[   28.589861] usb 3-2: New USB device found, idVendor=1d5c, idProduct=5801, bcdDevice= 1.01
[   28.589864] usb 3-2: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[   28.589865] usb 3-2: Product: USB2.0 Hub
[   28.589866] usb 3-2: Manufacturer: Fresco Logic, Inc.

Since Goshen Ridge is pretty stable in Linux I'm kind of suspecting still a
connection issue rather than SW. Or could be power related too. AFAIK the
USB 2.x should be rock solid but here it seems not. Are you using active or
passive cables and do they have the lightning logo?

You could still try to comment out both tb_retimer_scan() calls and see if
that makes any difference but I doubt since your last log unplug happened
when we were reading DROM of the second device router not when sidband
access was done.