usb: dwc3: gadget: use allocated/queued reqs for LST bit

Let's only set LST bit when we run out of space in
our TRB ring. For all other cases, we keep LST bit
unset which will prevent constant allocation and
deallocation of endpoint transfer resources.
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc3/gadget.c

@@ -897,7 +897,8 @@ static u32 dwc3_calc_trbs_left(struct dwc3_ep *dep)
 }
 
 static void dwc3_prepare_one_trb_sg(struct dwc3_ep *dep,
-		struct dwc3_request *req, unsigned int trbs_left)
+		struct dwc3_request *req, unsigned int trbs_left,
+		unsigned int more_coming)
 {
 	struct usb_request *request = &req->request;
 	struct scatterlist *sg = request->sg;
@@ -914,7 +915,8 @@ static void dwc3_prepare_one_trb_sg(struct dwc3_ep *dep,
 		dma = sg_dma_address(s);
 
 		if (sg_is_last(s)) {
-			if (list_is_last(&req->list, &dep->pending_list))
+			if (usb_endpoint_xfer_int(dep->endpoint.desc) ||
+				!more_coming)
 				last = true;
 
 			chain = false;
@@ -935,7 +937,8 @@ static void dwc3_prepare_one_trb_sg(struct dwc3_ep *dep,
 }
 
 static void dwc3_prepare_one_trb_linear(struct dwc3_ep *dep,
-		struct dwc3_request *req, unsigned int trbs_left)
+		struct dwc3_request *req, unsigned int trbs_left,
+		unsigned int more_coming)
 {
 	unsigned int	last = false;
 	unsigned int	length;
@@ -948,7 +951,7 @@ static void dwc3_prepare_one_trb_linear(struct dwc3_ep *dep,
 		last = true;
 
 	/* Is this the last request? */
-	if (list_is_last(&req->list, &dep->pending_list))
+	if (usb_endpoint_xfer_int(dep->endpoint.desc) || !more_coming)
 		last = true;
 
 	dwc3_prepare_one_trb(dep, req, dma, length,
@@ -966,6 +969,7 @@ static void dwc3_prepare_one_trb_linear(struct dwc3_ep *dep,
 static void dwc3_prepare_trbs(struct dwc3_ep *dep)
 {
 	struct dwc3_request	*req, *n;
+	unsigned int		more_coming;
 	u32			trbs_left;
 
 	BUILD_BUG_ON_NOT_POWER_OF_2(DWC3_TRB_NUM);
@@ -974,11 +978,15 @@ static void dwc3_prepare_trbs(struct dwc3_ep *dep)
 	if (!trbs_left)
 		return;
 
+	more_coming = dep->allocated_requests - dep->queued_requests;
+
 	list_for_each_entry_safe(req, n, &dep->pending_list, list) {
 		if (req->request.num_mapped_sgs > 0)
-			dwc3_prepare_one_trb_sg(dep, req, trbs_left--);
+			dwc3_prepare_one_trb_sg(dep, req, trbs_left--,
+					more_coming);
 		else
-			dwc3_prepare_one_trb_linear(dep, req, trbs_left--);
+			dwc3_prepare_one_trb_linear(dep, req, trbs_left--,
+					more_coming);
 
 		if (!trbs_left)
 			return;