linux-kernel - [REGRESSION] Thunderbolt Host Reset Change Causes eGPU Disconnection from 6.8.7=>6.8.8

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Date: Sun, 05 May 2024 01:12:06 +0000
From: Micha Albert <kernel@...ha.zone>
To: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc: "regressions@...ts.linux.dev" <regressions@...ts.linux.dev>
Subject: [REGRESSION] Thunderbolt Host Reset Change Causes eGPU Disconnection from 6.8.7=>6.8.8

Hello,

I have an AMD Radeon 6600 XT GPU in a cheap Thunderbolt eGPU board. In 6.8.7, this works as expected, and my Plymouth screen (including the LUKS password prompt) shows on my 2 monitors connected to the GPU as well as my main laptop screen. Upon entering the password, I'm put into userspace as expected. However, upon upgrading to 6.8.8, I will be greeted with the regular password prompt, but after entering my password and waiting for it to be accepted, my eGPU will reset and not function. I can tell that it resets since I can hear the click of my ATX power supply turning off and on again, and the status LED of the eGPU board goes from green to blue and back to green, all in less than a second.

I talked to a friend, and we found out that the kernel parameter thunderbolt.host_reset=false fixes the issue. He also thinks that commits cc4c94 (59a54c upstream) and 11371c (ec8162 upstream) look suspicious. I've attached the output of dmesg when the error was occurring, since I'm still able to use my laptop normally when this happens, just not with my eGPU and its connected displays.

Sincerely,
Micha Albert
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