usb: dwc3: gadget: start requests as soon as they come

In an attempt to make dwc3 slightly faster, let's
start usb_requests as soon as they come as that will
let us avoid a XFER_NOT_READY event and save a little
bit of time.

Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/dwc3/gadget.c

@@ -1071,6 +1071,22 @@ static int __dwc3_gadget_ep_queue(struct dwc3_ep *dep, struct dwc3_request *req)
 
 	list_add_tail(&req->list, &dep->request_list);
 
+	/*
+	 * If there are no pending requests and the endpoint isn't already
+	 * busy, we will just start the request straight away.
+	 *
+	 * This will save one IRQ (XFER_NOT_READY) and possibly make it a
+	 * little bit faster.
+	 */
+	if (!usb_endpoint_xfer_isoc(dep->endpoint.desc) &&
+			!(dep->flags & DWC3_EP_BUSY)) {
+		ret = __dwc3_gadget_kick_transfer(dep, 0, true);
+		if (ret && ret != -EBUSY)
+			dev_dbg(dwc->dev, "%s: failed to kick transfers\n",
+					dep->name);
+		return ret;
+	}
+
 	/*
 	 * There are a few special cases:
 	 *