[RFT PATCH 0/2] xhci: clean up endpoint rings after disconnect detect

[Mathias Nyman <mathias.nyman@linux.intel.com>]

Yiyu Zhou wrote PATCH 1/2, fixing a regression in USB HID device
enumeration caused by the endpoint recovery prevention code added in
v7.3-rc1. Some HID devices that used to enumerate after a brief
disconnect during enumeration now got stuck until URBs timed out.

PATCH 1/2 gives back the pending URBs right away, which solves most of
the problem, but it leaves the TRBs of the given back URBs on the ep0
ring. ep0 survives a brief disconnect during a port reset, so the xHC
may later process those TRBs during an enumeration retry, writing into
buffers that were already given back, or ep0 stays halted and the next
control transfer times out.

PATCH 2/2 cleans up the ep0 ring by resetting ep0 and moving its
dequeue pointer past the cancelled TDs, even if a disconnect or link
error is detected. Only Reset Endpoint and Set TR Dequeue Pointer
commands are issued; ep0 is not restarted while the disconnect is
pending. The rapid endpoint reset, restart and stop sequence that made
some xHC hosts fail Stop Endpoint commands is still avoided. Other
endpoints are still given back without resetting them, but their TRBs
are turned into no-ops first.

If you have seen the HID enumeration issue, or the xHC Stop Endpoint
failures with rapid endpoint state changes, testing these two patches
would be greatly appreciated.

If these patches work, they might be squashed into one before going
upstream.

[This message, and PATCH 2/2 commit message were cleaed up by LLM,
Code is still 'organic'.]

Thanks
Mathias

Mathias Nyman (1):
  xhci: clean up ep0 ring after disconnect instead of leaving stale TRBs

Yiyu Zhou (1):
  xhci: give back all TDs when skipping endpoint reset after disconnect

 drivers/usb/host/xhci-ring.c | 71 ++++++++++++++++++++++++++++++------
 drivers/usb/host/xhci.c      | 13 ++++---
 2 files changed, 67 insertions(+), 17 deletions(-)

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2.43.0