[Bug 221184] mouse/keyboard (connected via hub) usb reset under system load with weak cpu

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=221184

--- Comment #16 from Roman Elshin (roxmail@list.ru) ---
> Re comment #8: Are you sure that other operating system versions really are
> working fine?  Have you tried collecting a usbmon trace under another OS
> version while running your load test, and looking through the trace for -71
> errors?

Error reason are -EPROTO from ehci, and at least for mouse was introduced by
64cc3f12d1c7dd054a215bc1ff9cc2abcfe35832, reverting this fixing at least mouse
resets (need retest with current kernel), looking at code i am wonder if it
ever correct, code part (ehci-q.c):
---------------------------------------------------------------------------
                /*
                 * When MMF is active and PID Code is IN, queue is halted.
                 * EHCI Specification, Table 4-13.
                 */
                } else if ((token & QTD_STS_MMF) &&
                                        (QTD_PID(token) == PID_CODE_IN)) {
                        status = -EPROTO;
                /* CERR nonzero + halt --> stall */
                } else if (QTD_CERR(token)) {
                        status = -EPIPE;

                /* In theory, more than one of the following bits can be set
                 * since they are sticky and the transaction is retried.
                 * Which to test first is rather arbitrary.
                 */
                } else if (token & QTD_STS_MMF) {
                        /* fs/ls interrupt xfer missed the complete-split */
                        status = -EPROTO;
-----------------------------------------------------------------------------
why additional check:

((token & QTD_STS_MMF) && (QTD_PID(token) == PID_CODE_IN))

needed here (it was introduced by 64cc3f12d1c7dd054a215bc1ff9cc2abcfe35832),
there are (token & QTD_STS_MMF) already check with same return status later ?

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