[PATCH 0/2] xhci: handshake timeout overrun and configure endpoint hang on device disconnect

[Henry Tseng <henrytseng@qnap.com>]

This series addresses two problems found while debugging an AMD Raven
USB 3.1 xHCI (1022:15e0) that gets declared dead when a USB storage
enclosure is unplugged. During teardown a command fails to complete,
aborting the command ring also fails, and the whole host is declared
dead, taking unrelated devices on other root ports down with it:

  xhci_hcd 0000:0c:00.3: Command timeout, USBSTS: 0x00000010 PCD
  xhci_hcd 0000:0c:00.3: Abort command ring
  xhci_hcd 0000:0c:00.3: Abort failed to stop command ring: -110
  xhci_hcd 0000:0c:00.3: xHCI host controller not responding, assume dead

Reproduced on mainline v7.3-rc5:

  CPU:        AMD Ryzen Embedded V1500B
  xHCI:       AMD Raven USB 3.1, 0000:0c:00.3 [1022:15e0]
  Enclosure:  QNAP TL-D800C

I have only seen this with this enclosure on this controller. Other USB
devices unplug cleanly from the same host, and this enclosure unplugs
cleanly from a Meteor Lake-P xHCI. Similar messages were reported in
[1][2] without a resolution. I could not confirm the same command was
involved.

Patch 2 fixes the host death on disconnect. The command that never
completed is a configure endpoint command issued during teardown of a
device behind the disconnected root port, right before disable slot for
the same slot. Skip it when the roothub port is gone, as
xhci_check_bandwidth() already does when the host is being removed.

Patch 1 is an independent handshake overrun noticed during the same
debugging, and does not fix the disconnect hang on its own. The command
abort handshake has a 5 s timeout but took 15.8 s with interrupts
disabled. This is not specific to this controller. When forced to time
out, a 10 s xhci_handshake() returns after 19.1 s on Alder Lake-S and
17.2 s on Meteor Lake-P. With patch 1 applied it returns after 10 s on
both.

[1] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1857385
[2] https://marc.info/?l=linux-usb&m=155120372130870&w=2

Henry Tseng (2):
  xhci: make xhci_handshake() timeout wall-clock based again
  xhci: skip configure endpoint when dropping endpoints of a
    disconnected device

 drivers/usb/host/xhci.c | 30 ++++++++++++++++++++++--------
 1 file changed, 22 insertions(+), 8 deletions(-)

-- 
2.43.0