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Date: Thu, 23 May 2024 07:45:07 +0300
From: Mika Westerberg <mika.westerberg@linux.intel.com>
To: Mario Limonciello <mario.limonciello@amd.com>
Cc: Gia <giacomo.gio@gmail.com>, "S, Sanath" <Sanath.S@amd.com>,
	Benjamin =?utf-8?Q?B=C3=B6hmke?= <benjamin@boehmke.net>,
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	Linux regressions mailing list <regressions@lists.linux.dev>,
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	Andreas Noever <andreas.noever@gmail.com>,
	Michael Jamet <michael.jamet@intel.com>,
	Yehezkel Bernat <YehezkelShB@gmail.com>,
	"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>
Subject: Re: [REGRESSION][BISECTED] "xHCI host controller not responding,
 assume dead" on stable kernel > 6.8.7
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On Wed, May 22, 2024 at 10:19:51AM -0500, Mario Limonciello wrote:
> On 5/22/2024 09:41, Gia wrote:
> > Now this is odd...
> > 
> > I've tested another cable - a very short one used with a Gen3 nvme
> > enclosure that I'm sure it's working - and I got Gen2 20 Gbps. I also
> > have tested this on Windows 11 and I still just got a Gen2 connection.
> > 
> > I was almost sure it was caused by a bad USB4 implementation by the PC
> > manufacturer, then I tried to connect a Thunderbolt 3 disk enclosure
> > via daisy chain to the Caldigit dock and I got the full Gen3 40 Gbps
> > connection! See the attached picture.
> > 
> 
> I suspect you can't actually get Gen 3 performance in this configuration.
> IIUC you should still be limited by the uplink to the host.

One "explanation" could be that the distance from the SoC to the Type-C
connector is relatively long which would require a retimer to get the
Gen3 speeds.