usb: dwc3: gadget: Disable GUSB2PHYCFG.SUSPHY for End Transfer

If there's a disconnection while operating in eSS, there may be a delay
in VBUS drop response from the connector. In that case, the internal
link state may drop to operate in usb2 speed while the controller thinks
the VBUS is still high. The driver must make sure to disable
GUSB2PHYCFG.SUSPHY when sending endpoint command while in usb2 speed.
The End Transfer command may be called, and only that command needs to
go through at this point. Let's keep it simple and unconditionally
disable GUSB2PHYCFG.SUSPHY whenever we issue the command.

This scenario is not seen in real hardware. In a rare case, our
prototype type-c controller/interface may have a slow response
triggerring this issue.

Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/5651117207803c26e2f22ddf4e5ce9e865dcf7c7.1668045468.git.Thinh.Nguyen@synopsys.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Thinh Nguyen

drivers/usb/dwc3/gadget.c

@@ -291,7 +291,8 @@ int dwc3_send_gadget_ep_cmd(struct dwc3_ep *dep, unsigned int cmd,
 	 *
 	 * DWC_usb3 3.30a and DWC_usb31 1.90a programming guide section 3.2.2
 	 */
-	if (dwc->gadget->speed <= USB_SPEED_HIGH) {
+	if (dwc->gadget->speed <= USB_SPEED_HIGH ||
+	    DWC3_DEPCMD_CMD(cmd) == DWC3_DEPCMD_ENDTRANSFER) {
 		reg = dwc3_readl(dwc->regs, DWC3_GUSB2PHYCFG(0));
 		if (unlikely(reg & DWC3_GUSB2PHYCFG_SUSPHY)) {
 			saved_config |= DWC3_GUSB2PHYCFG_SUSPHY;