If a device connected to an xHCI host controller disconnects from the USB bus
and then reconnects, e.g. triggered by a firmware update, then the host
controller automatically activates the connection and the port is enabled. The
implementation of hub_port_connect_change() assumes that if the port is
enabled then nothing has changed. There is no check if the USB descriptors
have changed. As a result, the kernel's internal copy of the descriptors ends
up being incorrect and the device doesn't work properly anymore.

The solution to the problem is for hub_port_connect_change() always to
check whether the device's descriptors have changed before resuscitating
an enabled port.
Signed-off-by: David Heinzelmann <heinzelmann.david@gmail.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/20191009044647.24536-1-heinzelmann.david@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>