[PATCH RESEND wireless 3/4] wifi: rtl8xxxu: preserve RX requests across recoverable transfer errors

rtl8xxxu normally reuses 32 RX URBs, scheduling the submission worker when
more than eight completed requests have accumulated on the pending list.
Completion errors free URBs instead. A finite error burst can therefore
leave eight or fewer requests, which cannot reach that threshold after
they all complete. With no request in flight and no worker pending or
running, RX stays stopped even after the errors cease.

To prevent these errors from shrinking the pool below the number
needed for normal resubmission, retain URBs after EPROTO, EILSEQ, ETIME,
EOVERFLOW, ECOMM and ENOSR completions. EHCI can report ENOSR for IN data-buffer
errors, and FHCI maps RX buffer overrun to ECOMM. Free the failed
transfer's skb and keep its URB on a separate retry list.

Keeping the URBs is only part of the fix: the driver must also submit
them again without waiting for nine requests to accumulate. When the
first failed request enters the retry list, schedule delayed work for
100 ms. Further failures join that list while the work is pending.
When it runs, move the collected requests to normal pending and schedule
the submission worker even if only one request is waiting. Keeping
failed requests separate until then prevents normal completions from
triggering an immediate retry; successful RX keeps its existing batching.

A retry can itself fail with ENOMEM/EAGAIN. Returning that request to
normal pending would bring back the same threshold problem, so route
temporary submission failures from both start and the RX worker through
the delayed retry list as well.

Serialize retry insertion and scheduling with shutdown so late
completions cannot schedule fresh retries during stop. Cancel retry work
first, then wait for submission work before killing active URBs, so a
running worker cannot submit a request after the active requests have
been drained.

Cancellation and removal keep their release behavior. EPIPE endpoint-halt
recovery remains outside this change because it requires quiescing
requests and distinguishing recovery cancellation from shutdown.

Fixes: 26f1fad29ad9 ("New driver: rtl8xxxu (mac80211)")
Assisted-by: GPT-6 Astra
Signed-off-by: kimwooseok <redacted>
---
 drivers/net/wireless/realtek/rtl8xxxu/core.c  | 71 +++++++++++++++++--
 .../net/wireless/realtek/rtl8xxxu/rtl8xxxu.h  |  3 +
 2 files changed, 70 insertions(+), 4 deletions(-)