[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 #38 from Michał Pecio (michal.pecio@gmail.com) ---
(In reply to Paul Ausbeck from comment #31)
> Created attachment 308613 [details]
> xhci_hcd and usbcore dmesg trace, emb-qm77, S/R, USB storage manually
> disconnected
> 
> This is a dmesg log fragment with xhci_hcd and usbcore dynamic debug
> enabled, suspend/resume events, with the USB storage device being physically
> unplugged wile the machine is suspended.

This nicely illustrates why usb_persist is hard (and dangerous: you could
disconnect the device and connect a different one). This log is *exactly* the
same as the one you posted before, except that when the kernel restores power,
the root hub port goes to RxDetect state (detecting electrical SuperSpeed
connection) and stays there because the device is gone.

[  368.488920] xhci_hcd 0000:00:14.0: Set port 4-2 link state, portsc: 0x1203,
write 0x11261
[  368.859068] xhci_hcd 0000:00:14.0: Port change event, 4-2, id 6, portsc:
0x100080
[  369.862706] xhci_hcd 0000:00:14.0: set port power 4-2 ON, portsc: 0x100080
[  369.966674] xhci_hcd 0000:00:14.0: Get port status 4-2 read: 0x1002a0,
return 0x802a0

I suspect that usb_persist fails in this case because it simply doesn't
consider overcurrent ports to be eligible, or something like that.

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