To perform SuperSpeed compliance testing the port should first
be placed into compliance mode. For xHCI 1.0 and prior this
transition happens automatically when the port is in Training
and encounters an LFPS timeout. Thus running compliance tests
against a test appliance may simply just work by simply plugging
in to the downstream port.

However starting with xHCI 1.1 the transition from Polling.LFPS
to compliance mode may be disabled by default and needs to be
explicitly enabled by writing to the PLS field of the PORTSC
register, which sets an internal 'CTE' (Compliance Transition
Enabled) flag so that the port will perform the transition the
next time it encounters LFPS timeout. Whether this is disabled or
not is determined by the 'CTC' (Compliance Transition Capability)
bit in the HCCPARAMS2 capability register.

In order to allow a test operator to change this if needed, allow
a test driver (such as drivers/usb/misc/lvstest.c) to send a
SET_FEATURE(PORT_LINK_STATE) control message to the root hub to
update the link state prior to connecting to the port. Subsequently,
placing the port in warm reset would then disable the flag.
Signed-off-by: Jack Pham <jackp@codeaurora.org>
Acked-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>