usb: dwc3: gadget: Cleanup SG handling

The current logic in dwc3 driver is tracking req->num_queued_sgs and
req->sg. But they can be checked base on the num_pending_sgs and
num_trbs. They are redundant and can complicate the SG logic. Let's
remove them.

Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/96c7bf8f6b3e91e607d5b78ea51cb1d00c614eaf.1731545781.git.Thinh.Nguyen@synopsys.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Thinh Nguyen

drivers/usb/dwc3/core.h

@@ -941,10 +941,8 @@ struct dwc3_hwparams {
  * @request: struct usb_request to be transferred
  * @list: a list_head used for request queueing
  * @dep: struct dwc3_ep owning this request
- * @sg: pointer to first incomplete sg
  * @start_sg: pointer to the sg which should be queued next
  * @num_pending_sgs: counter to pending sgs
- * @num_queued_sgs: counter to the number of sgs which already got queued
  * @remaining: amount of data remaining
  * @status: internal dwc3 request status tracking
  * @epnum: endpoint number to which this request refers
@@ -964,7 +962,6 @@ struct dwc3_request {
 	struct scatterlist	*start_sg;
 
 	unsigned int		num_pending_sgs;
-	unsigned int		num_queued_sgs;
 	unsigned int		remaining;
 
 	unsigned int		status;

drivers/usb/dwc3/gadget.c

@@ -1544,7 +1544,6 @@ static int dwc3_prepare_trbs_sg(struct dwc3_ep *dep,
 		if (!last_sg)
 			req->start_sg = sg_next(s);
 
-		req->num_queued_sgs++;
 		req->num_pending_sgs--;
 
 		/*
@@ -1625,9 +1624,7 @@ static int dwc3_prepare_trbs(struct dwc3_ep *dep)
 		if (ret)
 			return ret;
 
-		req->sg			= req->request.sg;
-		req->start_sg		= req->sg;
-		req->num_queued_sgs	= 0;
+		req->start_sg		= req->request.sg;
 		req->num_pending_sgs	= req->request.num_mapped_sgs;
 
 		if (req->num_pending_sgs > 0) {
@@ -3472,40 +3469,26 @@ static int dwc3_gadget_ep_reclaim_trb_sg(struct dwc3_ep *dep,
 		int status)
 {
 	struct dwc3_trb *trb;
-	struct scatterlist *sg = req->sg;
-	struct scatterlist *s;
-	unsigned int num_queued = req->num_queued_sgs;
+	unsigned int num_completed_trbs = req->num_trbs;
 	unsigned int i;
 	int ret = 0;
 
-	for_each_sg(sg, s, num_queued, i) {
+	for (i = 0; i < num_completed_trbs; i++) {
 		trb = &dep->trb_pool[dep->trb_dequeue];
 
-		req->sg = sg_next(s);
-		req->num_queued_sgs--;
-
 		ret = dwc3_gadget_ep_reclaim_completed_trb(dep, req,
-				trb, event, status, true);
+				trb, event, status,
+				!!(trb->ctrl & DWC3_TRB_CTRL_CHN));
 		if (ret)
 			break;
 	}
 
 	return ret;
 }
 
-static int dwc3_gadget_ep_reclaim_trb_linear(struct dwc3_ep *dep,
-		struct dwc3_request *req, const struct dwc3_event_depevt *event,
-		int status)
-{
-	struct dwc3_trb *trb = &dep->trb_pool[dep->trb_dequeue];
-
-	return dwc3_gadget_ep_reclaim_completed_trb(dep, req, trb,
-			event, status, false);
-}
-
 static bool dwc3_gadget_ep_request_completed(struct dwc3_request *req)
 {
-	return req->num_pending_sgs == 0 && req->num_queued_sgs == 0;
+	return req->num_pending_sgs == 0 && req->num_trbs == 0;
 }
 
 static int dwc3_gadget_ep_cleanup_completed_request(struct dwc3_ep *dep,
@@ -3515,24 +3498,13 @@ static int dwc3_gadget_ep_cleanup_completed_request(struct dwc3_ep *dep,
 	int request_status;
 	int ret;
 
-	if (req->request.num_mapped_sgs)
-		ret = dwc3_gadget_ep_reclaim_trb_sg(dep, req, event,
-				status);
-	else
-		ret = dwc3_gadget_ep_reclaim_trb_linear(dep, req, event,
-				status);
+	ret = dwc3_gadget_ep_reclaim_trb_sg(dep, req, event, status);
 
 	req->request.actual = req->request.length - req->remaining;
 
 	if (!dwc3_gadget_ep_request_completed(req))
 		goto out;
 
-	if (req->needs_extra_trb) {
-		ret = dwc3_gadget_ep_reclaim_trb_linear(dep, req, event,
-				status);
-		req->needs_extra_trb = false;
-	}
-
 	/*
 	 * The event status only reflects the status of the TRB with IOC set.
 	 * For the requests that don't set interrupt on completion, the driver