usb: dwc3: gadget: extract __dwc3_prepare_one_trb()

This new internal function will be used to solve a minor issue with dwc3
which exists in regards to short packets with OUT endpoints. Currently
we're asking gadget driver to *always* send us aligned requests; however
if we have enough TRBs we can easily append one extra TRB chained to the
previous and keep a throw away 1024 byte buffer around for that.

The actual fix will come in a separate patch, this is merely in
preparation for such fix.
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc3/gadget.c

@@ -833,29 +833,13 @@ static void dwc3_gadget_ep_free_request(struct usb_ep *ep,
 
 static u32 dwc3_calc_trbs_left(struct dwc3_ep *dep);
 
-/**
- * dwc3_prepare_one_trb - setup one TRB from one request
- * @dep: endpoint for which this request is prepared
- * @req: dwc3_request pointer
- */
-static void dwc3_prepare_one_trb(struct dwc3_ep *dep,
-		struct dwc3_request *req, unsigned chain, unsigned node)
+static void __dwc3_prepare_one_trb(struct dwc3_ep *dep, struct dwc3_trb *trb,
+		dma_addr_t dma, unsigned length, unsigned chain, unsigned node,
+		unsigned stream_id, unsigned short_not_ok, unsigned no_interrupt)
 {
-	struct dwc3_trb		*trb;
 	struct dwc3		*dwc = dep->dwc;
 	struct usb_gadget	*gadget = &dwc->gadget;
 	enum usb_device_speed	speed = gadget->speed;
-	unsigned		length = req->request.length;
-	dma_addr_t		dma = req->request.dma;
-
-	trb = &dep->trb_pool[dep->trb_enqueue];
-
-	if (!req->trb) {
-		dwc3_gadget_move_started_request(req);
-		req->trb = trb;
-		req->trb_dma = dwc3_trb_dma_offset(dep, trb);
-		dep->queued_requests++;
-	}
 
 	dwc3_ep_inc_enq(dep);
 
@@ -901,11 +885,11 @@ static void dwc3_prepare_one_trb(struct dwc3_ep *dep,
 	if (usb_endpoint_dir_out(dep->endpoint.desc)) {
 		trb->ctrl |= DWC3_TRB_CTRL_CSP;
 
-		if (req->request.short_not_ok)
+		if (short_not_ok)
 			trb->ctrl |= DWC3_TRB_CTRL_ISP_IMI;
 	}
 
-	if ((!req->request.no_interrupt && !chain) ||
+	if ((!no_interrupt && !chain) ||
 			(dwc3_calc_trbs_left(dep) == 0))
 		trb->ctrl |= DWC3_TRB_CTRL_IOC;
 
@@ -913,13 +897,43 @@ static void dwc3_prepare_one_trb(struct dwc3_ep *dep,
 		trb->ctrl |= DWC3_TRB_CTRL_CHN;
 
 	if (usb_endpoint_xfer_bulk(dep->endpoint.desc) && dep->stream_capable)
-		trb->ctrl |= DWC3_TRB_CTRL_SID_SOFN(req->request.stream_id);
+		trb->ctrl |= DWC3_TRB_CTRL_SID_SOFN(stream_id);
 
 	trb->ctrl |= DWC3_TRB_CTRL_HWO;
 
 	trace_dwc3_prepare_trb(dep, trb);
 }
 
+/**
+ * dwc3_prepare_one_trb - setup one TRB from one request
+ * @dep: endpoint for which this request is prepared
+ * @req: dwc3_request pointer
+ * @chain: should this TRB be chained to the next?
+ * @node: only for isochronous endpoints. First TRB needs different type.
+ */
+static void dwc3_prepare_one_trb(struct dwc3_ep *dep,
+		struct dwc3_request *req, unsigned chain, unsigned node)
+{
+	struct dwc3_trb		*trb;
+	unsigned		length = req->request.length;
+	unsigned		stream_id = req->request.stream_id;
+	unsigned		short_not_ok = req->request.short_not_ok;
+	unsigned		no_interrupt = req->request.no_interrupt;
+	dma_addr_t		dma = req->request.dma;
+
+	trb = &dep->trb_pool[dep->trb_enqueue];
+
+	if (!req->trb) {
+		dwc3_gadget_move_started_request(req);
+		req->trb = trb;
+		req->trb_dma = dwc3_trb_dma_offset(dep, trb);
+		dep->queued_requests++;
+	}
+
+	__dwc3_prepare_one_trb(dep, trb, dma, length, chain, node,
+			stream_id, short_not_ok, no_interrupt);
+}
+
 /**
  * dwc3_ep_prev_trb() - Returns the previous TRB in the ring
  * @dep: The endpoint with the TRB ring