The USB2.0 spec chapter 11.24.2.13 says that the USB port which is going
under test needs to be put in suspend state before sending the test
command. Many hubs, don't enforce this precondition and they work fine
without this step. But there are some "special" hubs, which requires to
disable the port power before sending the test command.
Because the USB spec mention that the port should be suspended, also
do this step before sending the test command. This could rise the
problem with other hubs which are not compliant with the spec and the
test command will not work if the port is suspend. If such hubs are
found, a similar workaround like the disable part could be implemented
to skip the suspend port command.
Signed-off-by: Razvan Heghedus <heghedus.razvan@gmail.com>
Link: https://lore.kernel.org/r/20210915121615.3790-1-heghedus.razvan@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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