usb: dwc3: gadget: use link TRB for all endpoint types

instead of limiting link TRB only to Isoc endpoints,
let's use it for all endpoint types, this way we are
more likely to transfer more data before a
XferComplete event.
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc3/gadget.c

@@ -177,8 +177,7 @@ void dwc3_gadget_giveback(struct dwc3_ep *dep, struct dwc3_request *req,
 			 * DWC3_TRBCTL_LINK_TRB because it points the TRB we
 			 * just completed (not the LINK TRB).
 			 */
-			if (dwc3_ep_is_last_trb(dep->trb_dequeue) &&
-				usb_endpoint_xfer_isoc(dep->endpoint.desc))
+			if (dwc3_ep_is_last_trb(dep->trb_dequeue))
 				dwc3_ep_inc_deq(dep);
 		} while(++i < req->request.num_mapped_sgs);
 		req->started = false;
@@ -541,10 +540,10 @@ static int __dwc3_gadget_ep_enable(struct dwc3_ep *dep,
 		reg |= DWC3_DALEPENA_EP(dep->number);
 		dwc3_writel(dwc->regs, DWC3_DALEPENA, reg);
 
-		if (!usb_endpoint_xfer_isoc(desc))
+		if (usb_endpoint_xfer_control(desc))
 			goto out;
 
-		/* Link TRB for ISOC. The HWO bit is never reset */
+		/* Link TRB. The HWO bit is never reset */
 		trb_st_hw = &dep->trb_pool[0];
 
 		trb_link = &dep->trb_pool[DWC3_TRB_NUM - 1];
@@ -767,9 +766,8 @@ static void dwc3_prepare_one_trb(struct dwc3_ep *dep,
 	}
 
 	dwc3_ep_inc_enq(dep);
-	/* Skip the LINK-TRB on ISOC */
-	if (dwc3_ep_is_last_trb(dep->trb_enqueue) &&
-			usb_endpoint_xfer_isoc(dep->endpoint.desc))
+	/* Skip the LINK-TRB */
+	if (dwc3_ep_is_last_trb(dep->trb_enqueue))
 		dwc3_ep_inc_enq(dep);
 
 	trb->size = DWC3_TRB_SIZE_LENGTH(length);
@@ -836,52 +834,26 @@ static void dwc3_prepare_trbs(struct dwc3_ep *dep, bool starting)
 {
 	struct dwc3_request	*req, *n;
 	u32			trbs_left;
-	u32			max;
 	unsigned int		last_one = 0;
 
 	BUILD_BUG_ON_NOT_POWER_OF_2(DWC3_TRB_NUM);
 
-	/* the first request must not be queued */
 	trbs_left = dep->trb_dequeue - dep->trb_enqueue;
 
-	/* Can't wrap around on a non-isoc EP since there's no link TRB */
-	if (!usb_endpoint_xfer_isoc(dep->endpoint.desc)) {
-		max = DWC3_TRB_NUM - dep->trb_enqueue;
-		if (trbs_left > max)
-			trbs_left = max;
-	}
-
 	/*
-	 * If busy & slot are equal than it is either full or empty. If we are
-	 * starting to process requests then we are empty. Otherwise we are
+	 * If enqueue & dequeue are equal than it is either full or empty. If we
+	 * are starting to process requests then we are empty. Otherwise we are
 	 * full and don't do anything
 	 */
 	if (!trbs_left) {
 		if (!starting)
 			return;
+
 		trbs_left = DWC3_TRB_NUM;
-		/*
-		 * In case we start from scratch, we queue the ISOC requests
-		 * starting from slot 1. This is done because we use ring
-		 * buffer and have no LST bit to stop us. Instead, we place
-		 * IOC bit every TRB_NUM/4. We try to avoid having an interrupt
-		 * after the first request so we start at slot 1 and have
-		 * 7 requests proceed before we hit the first IOC.
-		 * Other transfer types don't use the ring buffer and are
-		 * processed from the first TRB until the last one. Since we
-		 * don't wrap around we have to start at the beginning.
-		 */
-		if (usb_endpoint_xfer_isoc(dep->endpoint.desc)) {
-			dep->trb_dequeue = 1;
-			dep->trb_enqueue = 1;
-		} else {
-			dep->trb_dequeue = 0;
-			dep->trb_enqueue = 0;
-		}
 	}
 
 	/* The last TRB is a link TRB, not used for xfer */
-	if ((trbs_left <= 1) && usb_endpoint_xfer_isoc(dep->endpoint.desc))
+	if (trbs_left <= 1)
 		return;
 
 	list_for_each_entry_safe(req, n, &dep->pending_list, list) {
@@ -1948,8 +1920,7 @@ static int dwc3_cleanup_done_reqs(struct dwc3 *dwc, struct dwc3_ep *dep,
 		i = 0;
 		do {
 			slot = req->first_trb_index + i;
-			if ((slot == DWC3_TRB_NUM - 1) &&
-				usb_endpoint_xfer_isoc(dep->endpoint.desc))
+			if (slot == DWC3_TRB_NUM - 1)
 				slot++;
 			slot %= DWC3_TRB_NUM;
 			trb = &dep->trb_pool[slot];