[Bug 218465] Linux warning `usb: port power management may be unreliable` on Dell XPS 13 9360

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=218465

--- Comment #2 from Mathias Nyman (mathias.nyman@linux.intel.com) ---
High-speed (HS) ans SuperSpeed (SS) ports are peered based on their Physical
Location Description (_PLD) object in ACPI tables.

The SSDT7 ACPI table dump shows that _PLD is created by calling a GPLD
helper method with some parameters. For High-Speed ports (HS0x) this seems
to be called with increasing port numer up to HS port 5. From port 6 onwards
all parameters are 0.

Scope (\_SB.PCI0.XHC.RHUB.HS01)
    Method (_PLD, 0, NotSerialized)  // _PLD: Physical Location of Device
        Return (GPLD (One, One))

Scope (\_SB.PCI0.XHC.RHUB.HS02)
    Method (_PLD, 0, NotSerialized)  // _PLD: Physical Location of Device
        Return (GPLD (One, 0x02))
...
Scope (\_SB.PCI0.XHC.RHUB.HS05)
    Method (_PLD, 0, NotSerialized)  // _PLD: Physical Location of Device
        Return (GPLD (Zero, 0x05))

Scope (\_SB.PCI0.XHC.RHUB.HS06)
    Method (_PLD, 0, NotSerialized)  // _PLD: Physical Location of Device
        Return (GPLD (Zero, Zero))

Scope (\_SB.PCI0.XHC.RHUB.HS07)
    Method (_PLD, 0, NotSerialized)  // _PLD: Physical Location of Device
        Return (GPLD (Zero, Zero))

For SuperSpeed ports (SS0x) the same is true. Ports 1-

Scope (\_SB.PCI0.XHC.RHUB.SS01)
    Method (_PLD, 0, NotSerialized)  // _PLD: Physical Location of Device
        Return (GPLD (One, One))

Scope (\_SB.PCI0.XHC.RHUB.SS02)
    Method (_PLD, 0, NotSerialized)  // _PLD: Physical Location of Device
        Return (GPLD (One, 0x02))

Scope (\_SB.PCI0.XHC.RHUB.SS03)
    Method (_PLD, 0, NotSerialized)  // _PLD: Physical Location of Device
        Return (GPLD (Zero, Zero))

Scope (\_SB.PCI0.XHC.RHUB.SS04)
    Method (_UPC, 0, NotSerialized)  // _UPC: USB Port Capabilities
        Return (GPLD (Zero, Zero))

Basically all HS port from 6 upwards and SS ports from 3 upwards report the
same _PLD, this messes up port peering and results in the following messages
during boot:  

usb usb2-port1: peered to usb1-port1
usb usb2-port2: peered to usb1-port2
usb usb2-port3: peered to usb1-port6
usb: failed to peer usb2-port4 and usb1-port6 by location (usb2-port4:none)
(usb1-port6:usb2-port3)
usb usb2-port4: failed to peer to usb1-port6 (-16)
usb: port power management may be unreliable
usb: failed to peer usb2-port5 and usb1-port6 by location (usb2-port5:none)
(usb1-port6:usb2-port3)
usb usb2-port5: failed to peer to usb1-port6 (-16)
usb: failed to peer usb2-port6 and usb1-port6 by location (usb2-port6:none)
(usb1-port6:usb2-port3)
usb usb2-port6: failed to peer to usb1-port6 (-16)

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