[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 #40 from Alan Stern (stern@rowland.harvard.edu) ---
For USB-2, mismatched toggles usually don't hurt.  Mismatches occur when an ACK
packet is lost, so the sender thinks its data wasn't received but the receiver
thinks it was.  When this happens, the sender will resend the same data using
the old toggle value; the receiver will note the mismatch and ignore the
duplicate data while acknowledging it.  This is part of the reason why the USB
stack historically has not included much error handling for EPROTO errors.

USB-3 is more complicated, and the host controller hardware keeps track of more
information that USB-2 host controllers do.  Re-establishing correct
synchronization after an error is therefore all the more difficult.  It would
be worth some effort to find a solution that can work for both USB-2 and USB-3.

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