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Date: Sun, 5 May 2024 09:17:58 -0500
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Subject: Re: [REGRESSION] Thunderbolt Host Reset Change Causes eGPU
 Disconnection from 6.8.7=>6.8.8
To: Mario Limonciello <superm1@gmail.com>,
 Linux regressions mailing list <regressions@lists.linux.dev>,
 Micha Albert <kernel@micha.zone>
Cc: "stable@vger.kernel.org" <stable@vger.kernel.org>,
 "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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From: Mario Limonciello <mario.limonciello@amd.com>
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On 5/5/2024 07:37, Mario Limonciello wrote:
> 
> 
> On 5/4/24 23:59, Linux regression tracking (Thorsten Leemhuis) wrote:
>> [CCing Mario, who asked for the two suspected commits to be backported]
>>
>> On 05.05.24 03:12, Micha Albert wrote:
>>>
>>>      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.
>>
>> Thx for the report. Could you please test if 6.9-rc6 (or a later
>> snapshot; or -rc7, which should be out in about ~18 hours) is affected
>> as well? That would be really important to know.
>>
>> It would also be great if you could try reverting the two patches you
>> mentioned and see if they are really what's causing this. There iirc are
>> two more; maybe you might need to revert some or all of them in the
>> order they were applied.
> 
> There are two other things that I think would be good to understand this 
> issue.
> 
> 1) Is it related to trusted devices handling?
> 
> You can try to apply it both to 6.8.y or to 6.9-rc.
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu.git/commit/?h=iommu/fixes&id=0f91d0795741c12cee200667648669a91b568735
> 
> 2) Is it because you have amdgpu in your initramfs but not thunderbolt?
> 
> If so; there's very likely an ordering issue.
> 
> [    2.325788] [drm] GPU posting now...
> [   30.360701] ACPI: bus type thunderbolt registered
> 
> Can you remove amdgpu from your initramfs and wait for it to startup 
> after you pivot rootfs?  Does this still happen?
> 

One more thought.  When you say it's "not function", is it authorized in 
thunderbolt sysfs?

See 
https://github.com/torvalds/linux/blob/master/Documentation/admin-guide/thunderbolt.rst

Is it showing up in lspci anymore?

>>
>> Ciao, Thorsten
>>
>> P.s.: To be sure the issue doesn't fall through the cracks unnoticed,
>> I'm adding it to regzbot, the Linux kernel regression tracking bot:
>>
>> #regzbot ^introduced v6.8.7..v6.8.8
>> #regzbot title thunderbolt: eGPU disconnected during boot
>>