[Bug 219748] Pluggable UD-4VPD dock appears to continually reset with AMD AI 365

bugzilla-daemon
2025-03-06T07:16:38Z

--- Comment #29 from Mika Westerberg (mika.westerberg@linux.intel.com) ---
For the first dmesg with "undetected" display the enumeration goes fine and the
DP tunnel is created however:

[ 54.496699] [drm] DPIA AUX failed on 0x0(1), error 3
[ 54.579780] [drm] DM_MST: starting TM on aconnector: 00000000a96810d6 [id:
133]
[ 54.587986] [drm] DM_MST: DP14, 4-lane link detected
[ 54.591410] [drm] DPIA AUX failed on 0x1000(5), error 3
[ 54.596690] [drm] DMUB HPD RX IRQ callback: link_index=7
[ 54.605700] [drm] DMUB HPD RX IRQ callback: link_index=7
[ 54.612512] [drm] DPIA AUX failed on 0x2003(1), error 3
[ 54.616646] [drm] DMUB HPD RX IRQ callback: link_index=7
[ 54.624654] [drm] DMUB HPD RX IRQ callback: link_index=7
[ 54.631037] [drm] DPIA AUX failed on 0x2002(4), error 3

Looks to me some sort of link training issue but as far as I can tell the DP
tunnel is up just fine. Immediately after this there is unplug:

[ 54.632887] thunderbolt 0000:c6:00.6: acking hot unplug event on 0:2
[ 54.632987] thunderbolt 1-0:2.1: retimer disconnected

I think this done by you and then replug. If that's the case then from USB4
perspective it looks okay (let me know if this is not the case). I'm leaving
the graphics side for Mario to comment on as I'm not qualified. I do see MST
and that seem to be problematic in Linux IIRC.

There is one more thing that need to check. Do you have
CONFIG_USB4_DEBUGFS_MARGINING=y set in your kernel .config? I ask because the
driver exposes the AMD retimer from the dock upstream port side too. It is okay
if you have that set but if not something is not right then.

Regarding the missing network adapter, what happened there is that the USB4
link did not come up at all so all you got is the USB 2.x wires and devices.
You see them "High Speed" and "Full Speed" in the dmesg. Now, this is something
outside of what software can fix. Typically it's the Power Delivery firmware
that handles this but most cases simply unplug plug or flipping the cable makes
it work.