usb: dwc3: gadget: tracking per-TRB remaining bytes

This will give us a simpler way of figuring out how
many bytes were left in each TRB. It's useful for
cases where we queue only part of an SG-list due to
amount of available TRBs at the time of kicking the
transfer.
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc3/core.h

@@ -715,6 +715,7 @@ struct dwc3_hwparams {
  * @dep: struct dwc3_ep owning this request
  * @sg: pointer to first incomplete sg
  * @num_pending_sgs: counter to pending sgs
+ * @remaining: amount of data remaining
  * @epnum: endpoint number to which this request refers
  * @trb: pointer to struct dwc3_trb
  * @trb_dma: DMA address of @trb
@@ -729,6 +730,7 @@ struct dwc3_request {
 	struct scatterlist	*sg;
 
 	unsigned		num_pending_sgs;
+	unsigned		remaining;
 	u8			epnum;
 	struct dwc3_trb		*trb;
 	dma_addr_t		trb_dma;

drivers/usb/dwc3/gadget.c

@@ -178,6 +178,7 @@ void dwc3_gadget_giveback(struct dwc3_ep *dep, struct dwc3_request *req,
 	req->started = false;
 	list_del(&req->list);
 	req->trb = NULL;
+	req->remaining = 0;
 
 	if (req->request.status == -EINPROGRESS)
 		req->request.status = status;
@@ -2014,7 +2015,7 @@ static int __dwc3_cleanup_done_trbs(struct dwc3 *dwc, struct dwc3_ep *dep,
 		return 1;
 
 	count = trb->size & DWC3_TRB_SIZE_MASK;
-	req->request.actual += count;
+	req->remaining += count;
 
 	if (dep->direction) {
 		if (count) {
@@ -2068,11 +2069,10 @@ static int dwc3_cleanup_done_reqs(struct dwc3 *dwc, struct dwc3_ep *dep,
 	struct dwc3_request	*req, *n;
 	struct dwc3_trb		*trb;
 	bool			ioc = false;
-	int			ret;
+	int			ret = 0;
 
 	list_for_each_entry_safe(req, n, &dep->started_list, list) {
 		unsigned length;
-		unsigned actual;
 		int chain;
 
 		length = req->request.length;
@@ -2100,17 +2100,10 @@ static int dwc3_cleanup_done_reqs(struct dwc3 *dwc, struct dwc3_ep *dep,
 					event, status, chain);
 		}
 
-		/*
-		 * We assume here we will always receive the entire data block
-		 * which we should receive. Meaning, if we program RX to
-		 * receive 4K but we receive only 2K, we assume that's all we
-		 * should receive and we simply bounce the request back to the
-		 * gadget driver for further processing.
-		 */
-		actual = length - req->request.actual;
-		req->request.actual = actual;
+		req->request.actual = length - req->remaining;
 
-		if (ret && chain && (actual < length) && req->num_pending_sgs)
+		if (ret && chain && (req->request.actual < length)
+				&& req->num_pending_sgs)
 			return __dwc3_gadget_kick_transfer(dep, 0);
 
 		dwc3_gadget_giveback(dep, req, status);