[Bug 220491] usb_storage connected SD card disconnects/reconnects on resume from suspend

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=220491

--- Comment #28 from Paul Ausbeck (paula@alumni.cse.ucsc.edu) ---
Michael, Mathias: I concur that the emb-qm77 machine has some sort of
hardware/BIOS bug. It does not matter what type of device is plugged into a USB
3.0 port, that device will always disconnect/reconnect during resume from
suspend and there will always be some kernel log entry related to overcurrent.
My feeling is that there is no actual overcurrent and that the overcurrent
detection mechanism is faulty. To me, the overcurrent detection is a
red-herring, it would be nice to keep the device stack together even if there
is a hardware bug. I think one salient point is that I personally own two
entirely different machines that both would benefit from the linux USB stack
keeping the device number the same across a suspend/resume related
disconnect/reconnect. If I have two such machines, statistically it is likely
that there are quite a few such machines out there. In fact, there may already
be another such machine in my collection, I just don't know it yet.

I will also say that it may be nicer/easier to keep the disconnect/reconnect
from happening, but my feeling just now is that that approach would likely be
more machine specific. What I'm trying to say is that allowing
disconnect/reconnect to happen and keeping port context to allow the device
number to remain unchanged may be a more general solution. It would be nice to
formulate a solution that would work across all members of the class of
disconnect/reconnects that occur for some reason other than physical
unplug/replug.

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