linux-kernel - Re: [PATCH v2 0/2] thunderbolt: Fix S4 resume incongruities

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Message-ID: <20260108114205.GS2275908@black.igk.intel.com>
Date: Thu, 8 Jan 2026 12:42:05 +0100
From: Mika Westerberg <mika.westerberg@...ux.intel.com>
To: Mario Limonciello <superm1@...nel.org>
Cc: "open list:THUNDERBOLT DRIVER" <linux-usb@...r.kernel.org>,
	linux-kernel@...r.kernel.org,
	Andreas Noever <andreas.noever@...il.com>,
	Michael Jamet <michael.jamet@...el.com>,
	Yehezkel Bernat <YehezkelShB@...il.com>
Subject: Re: [PATCH v2 0/2] thunderbolt: Fix S4 resume incongruities

On Wed, Jan 07, 2026 at 02:50:54PM -0600, Mario Limonciello wrote:
> On 1/7/26 3:33 AM, Mika Westerberg wrote:
> > Hi,
> > 
> > On Mon, Jan 05, 2026 at 11:37:47PM -0600, Mario Limonciello (AMD) wrote:
> > > When a machine is restored from S4 if the firmware CM has created
> > > tunnels there can be an incongruity of expectation from the kernel
> > > when compared to booting from S5.  This series addresses those.
> > 
> > I suspect there is no Firmware CM in AMD platforms so this actually means
> > the BIOS CM, correct?
> 
> That's correct.
> 
> > 
> > However, on S4 we actually do reset host router when the "boot kernel" is
> > started before loading and jumping to the hibernation image.
> 
> That's only if thunderbolt.ko is built into the kernel or is included in the
> initramfs before it does the pivot to the hibernation image.

Ah good point.

> At least in the tests we were doing it's not part of the boot kernel.
> 
> > It might be
> > that this boot kernel tunnel configuration is causing the issues you are
> > seeing (can you elaborate on those?)
> 
> The issues manifest "downstream" in the GPU driver.  There are a bunch of
> aux failures and a non functional display.  Tracing it back the GPU driver
> isn't alive at the time that the tunnels are attempted to be reconstructed
> at the moment and so CM tears DP tunnel down and then when GPU driver does
> come up it is not functional.
> 
> DP tunnel constructed at:
> 
> [  486.007194] thunderbolt 0000:c6:00.6: AUX RX path activation complete
> 
> First DPRx timeout at:
> 
> [  486.135483] thunderbolt 0000:c6:00.6: 0:6 <-> 2:13 (DP): DPRX read
> timeout
> 
> DP tunnel deactivating at:
> 
>  [  486.331856] thunderbolt 0000:c6:00.6: 0:6 <-> 2:13 (DP): deactivating

Hmm, we have dprx_timeout by default 12 seconds. How come it tears down the
tunnel already?

> 
> First DPRx DPCD reading starts at:
> 
> [  486.351765] amdgpu 0000:c4:00.0: amdgpu: [drm] DPIA AUX failed on
> 0xf0000(10), error 7

This would have maked it within the 12s if I read the timestamps right.