Re: [PATCH] [RFC] thunderbolt: Add delay for Dell U2725QE link width
From: Mario Limonciello
Date: Wed Dec 10 2025 - 16:42:52 EST
+Wayne
Here is the full thread since you're being added in late.
https://lore.kernel.org/linux-usb/20251209054141.1975982-1-acelan.kao@xxxxxxxxxxxxx/
On 12/10/25 1:41 AM, Mika Westerberg wrote:
Hi,
On Wed, Dec 10, 2025 at 11:15:25AM +0800, Chia-Lin Kao (AceLan) wrote:
We should understand the issue better. This is Intel Goshen Ridge basedActually, we encountered the same issue on Intel machine, too.
monitor which I'm pretty sure does not require additional quirks, at least
I have not heard any issues like this. I suspect this is combination of the
AMD and Intel hardware that is causing the issue.
Here is the log captured by my ex-colleague, and at that time he used
6.16-rc4 drmtip kernel and should have reported this issue somewhere.
https://paste.ubuntu.com/p/bJkBTdYMp6/
The log combines with drm debug log, and becomes too large to be
pasted on the pastebin, so I removed some unrelated lines between 44s
~ 335s.
Okay I see similar unplug there:
[ 337.429646] [374] thunderbolt:tb_handle_dp_bandwidth_request:2752: thunderbolt 0000:00:0d.2: 0:5: handling bandwidth allocation request, retry 0
...
[ 337.430291] [165] thunderbolt:tb_cfg_ack_plug:842: thunderbolt 0000:00:0d.2: acking hot unplug event on 0:1
We had an issue with MST monitors but that resulted unplug of the DP OUT
not link going down. That was fixed with:
9cb15478916e ("drm/i915/dp_mst: Work around Thunderbolt sink disconnect after SINK_COUNT_ESI read")
If you have Intel hardware still there it would be good if you could try
and provide trace from that as well.
If that does help; we could experiment with doing something similar in amdgpu too.
It would mean it's not really an iTBT DP-in adapter's firmware issue in that case.
Acelan,
If you want to try to port 9cb15478916e over the interrupt handler in amdgpu that needs the change I expect to be dp_read_hpd_rx_irq_data().