usb: dwc2: gadget: prevent new request submission during suspend

If usb controller is in partial power down, any write to registers may
cause unpredictable behavior.
Thus, prevent any new request submission once controller is in partial
power down.

Acked-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Gregory Herrero <gregory.herrero@intel.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
diff --git a/drivers/usb/dwc2/gadget.c b/drivers/usb/dwc2/gadget.c
index a360f49..732761f 100644
--- a/drivers/usb/dwc2/gadget.c
+++ b/drivers/usb/dwc2/gadget.c
@@ -790,6 +790,13 @@
 		ep->name, req, req->length, req->buf, req->no_interrupt,
 		req->zero, req->short_not_ok);
 
+	/* Prevent new request submission when controller is suspended */
+	if (hs->lx_state == DWC2_L2) {
+		dev_dbg(hs->dev, "%s: don't submit request while suspended\n",
+				__func__);
+		return -EAGAIN;
+	}
+
 	/* initialise status of the request */
 	INIT_LIST_HEAD(&hs_req->queue);
 	req->actual = 0;