On 14.2.2024 14.58, Mathias Nyman wrote:
On 14.2.2024 11.31, Paul Menzel wrote:
Dear Linux folks,
As a follow-up to *Linux warning `usb: port power management may be unreliable` on Dell XPS 13 9360* [1][2], Linux warns about this on Dell laptops, desktops, and servers, and also on devices from other manufacturers [3].
I created issue with corresponding Linux messages and output of acpidump attached for more devices I have access to:
1. Linux warning `usb: port power management may be unreliable` on Dell OptiPlex 3620
https://bugzilla.kernel.org/show_bug.cgi?id=218486
2. Linux warning `usb: port power management may be unreliable` on Dell OptiPlex 5055
https://bugzilla.kernel.org/show_bug.cgi?id=218487
3. Linux warning `usb: port power management may be unreliable` on OptiPlex Small Form Factor Plus 7010
https://bugzilla.kernel.org/show_bug.cgi?id=218488
4. Linux warning `usb: port power management may be unreliable` on Dell PowerEdge T440
https://bugzilla.kernel.org/show_bug.cgi?id=218490
(Artem (Cc:) marked them all as duplicates, and I asked him privately to undo this until the maintainers ask me to.)
Mathias was so kind to analyze the ACPI tables [2].
Is this a firmware issue or a Linux one? As a user I am unsure what to do, and ignoring warnings sounds wrong to me.
At a fist glance it looks like a firmware issue.
USB2 and USB3 ports are in this case matched and peered based on the ports
ACPI _PLD (Physical Device Location) entries.
Usually there is only one USB2 and one USB3 port with exactly the same _PLD values,
but here it appears more ports return similar _PLD values.
But need to look a bit deeper at this. Linux does not compare at all _PLD fields,
does not compare _all_ _PLD fields
and xhci specification Appendix D mentions mapping ports to connectors using
both port _UPC and _PLD ACPI entries.
Thanks
Mathias
