linux-kernel - Re: [PATCH v3] PCI: Prevent power state transition of erroneous device

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Message-ID: <aC3WESz-Jeox5_TA@wunner.de>
Date: Wed, 21 May 2025 15:33:05 +0200
From: Lukas Wunner <lukas@...ner.de>
To: Raag Jadav <raag.jadav@...el.com>
Cc: Denis Benato <benato.denis96@...il.com>,
	Mario Limonciello <superm1@...nel.org>, rafael@...nel.org,
	mahesh@...ux.ibm.com, oohall@...il.com, bhelgaas@...gle.com,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	ilpo.jarvinen@...ux.intel.com, aravind.iddamsetty@...ux.intel.com
Subject: Re: [PATCH v3] PCI: Prevent power state transition of erroneous
 device

On Thu, May 15, 2025 at 02:58:25PM +0300, Raag Jadav wrote:
> On Wed, May 14, 2025 at 11:25:36PM +0200, Denis Benato wrote:
> > >> You can see the dmesg here: https://pastebin.com/Um7bmdWi
> 
> Thanks for the report. From logs it looks like a hotplug event is triggered
> for presence detect which is disabling the slot and in turn loosing the
> device on resume. The cause of it is unclear though (assuming it is not
> a manual intervention).

Below the Root Port 0000:00:1a.0, there is a discrete Intel Thunderbolt
controller.  Attached to it is an ASMedia Thunderbolt controller.

The Presence Detect Changed event occurs at the Intel Thunderbolt
controller's Downstream Port.  Because PCIe is tunneled over Thunderbolt,
this means that the tunnel to the ASMedia controller could not be
re-established on resume, hence the Presence Detect Changed event.
Could be the result of the device being unplugged or some Thunderbolt
issue.

For the same reason, anything below the Intel Thunderbolt controller
is inaccessible on resume, hence the "Unable to change power state"
messages for the HDA controller on the AMD GPU.

Thanks,

Lukas