usb: dwc3: gadget: add trb enqueue/dequeue helpers

Add three little helpers which will aid in making
the code slightly easier to read. One helper
increments enqueue pointer, another increments
dequeue pointer and the last one tests if we're
dealing with the last TRB.
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc3/gadget.c

@@ -145,6 +145,21 @@ int dwc3_gadget_set_link_state(struct dwc3 *dwc, enum dwc3_link_state state)
 	return -ETIMEDOUT;
 }
 
+static void dwc3_ep_inc_enq(struct dwc3_ep *dep)
+{
+	dep->trb_enqueue++;
+}
+
+static void dwc3_ep_inc_deq(struct dwc3_ep *dep)
+{
+	dep->trb_dequeue++;
+}
+
+static int dwc3_ep_is_last_trb(unsigned int index)
+{
+	return (index % DWC3_TRB_NUM) == (DWC3_TRB_NUM - 1);
+}
+
 void dwc3_gadget_giveback(struct dwc3_ep *dep, struct dwc3_request *req,
 		int status)
 {
@@ -154,16 +169,15 @@ void dwc3_gadget_giveback(struct dwc3_ep *dep, struct dwc3_request *req,
 	if (req->started) {
 		i = 0;
 		do {
-			dep->trb_dequeue++;
+			dwc3_ep_inc_deq(dep);
 			/*
 			 * Skip LINK TRB. We can't use req->trb and check for
 			 * DWC3_TRBCTL_LINK_TRB because it points the TRB we
 			 * just completed (not the LINK TRB).
 			 */
-			if (((dep->trb_dequeue % DWC3_TRB_NUM) ==
-				DWC3_TRB_NUM - 1) &&
+			if (dwc3_ep_is_last_trb(dep->trb_dequeue) &&
 				usb_endpoint_xfer_isoc(dep->endpoint.desc))
-				dep->trb_dequeue++;
+				dwc3_ep_inc_deq(dep);
 		} while(++i < req->request.num_mapped_sgs);
 		req->started = false;
 	}
@@ -750,11 +764,11 @@ static void dwc3_prepare_one_trb(struct dwc3_ep *dep,
 		req->first_trb_index = dep->trb_enqueue % DWC3_TRB_NUM;
 	}
 
-	dep->trb_enqueue++;
+	dwc3_ep_inc_enq(dep);
 	/* Skip the LINK-TRB on ISOC */
-	if (((dep->trb_enqueue % DWC3_TRB_NUM) == DWC3_TRB_NUM - 1) &&
+	if (dwc3_ep_is_last_trb(dep->trb_enqueue) &&
 			usb_endpoint_xfer_isoc(dep->endpoint.desc))
-		dep->trb_enqueue++;
+		dwc3_ep_inc_enq(dep);
 
 	trb->size = DWC3_TRB_SIZE_LENGTH(length);
 	trb->bpl = lower_32_bits(dma);