usb: dwc3: gadget: Check for L1/L2/U3 for Start Transfer

usb: dwc3: gadget: Check for L1/L2/U3 for Start Transfer

commit 63c4c320ccf77074ffe9019ac596603133c1b517 upstream.

The programming guide noted that the driver needs to verify if the link
state is in U0 before executing the Start Transfer command. If it's not
in U0, the driver needs to perform remote wakeup. This is not accurate.
If the link state is in U1/U2, then the controller will not respond to
link recovery request from DCTL.ULSTCHNGREQ. The Start Transfer command
will trigger a link recovery if it is in U1/U2. A clarification will be
added to the programming guide for all controller versions.

The current implementation shouldn't cause any functional issue. It may
occasionally report an invalid time out warning from failed link
recovery request. The driver will still go ahead with the Start Transfer
command if the remote wakeup fails. The new change only initiates remote
wakeup where it is needed, which is when the link state is in L1/L2/U3.

Fixes: c36d8e947a56 ("usb: dwc3: gadget: put link to U0 before Start Transfer")
Cc: <stable@vger.kernel.org>
Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/05b4a5fbfbd0863fc9b1d7af934a366219e3d0b4.1635204761.git.Thinh.Nguyen@synopsys.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>