usb: dwc3: gadget: add support for SG lists

add support for SG lists on dwc3 driver. With
this we can e.g. use VFS layer's SG lists on
storage gadgets so that we can start bigger
transfers and improve throughput.
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/dwc3/gadget.c

@@ -65,6 +65,22 @@ void dwc3_map_buffer_to_dma(struct dwc3_request *req)
 		return;
 	}
 
+	if (req->request.num_sgs) {
+		int	mapped;
+
+		mapped = dma_map_sg(dwc->dev, req->request.sg,
+				req->request.num_sgs,
+				req->direction ? DMA_TO_DEVICE
+				: DMA_FROM_DEVICE);
+		if (mapped < 0) {
+			dev_err(dwc->dev, "failed to map SGs\n");
+			return;
+		}
+
+		req->request.num_mapped_sgs = mapped;
+		return;
+	}
+
 	if (req->request.dma == DMA_ADDR_INVALID) {
 		req->request.dma = dma_map_single(dwc->dev, req->request.buf,
 				req->request.length, req->direction
@@ -82,6 +98,17 @@ void dwc3_unmap_buffer_from_dma(struct dwc3_request *req)
 		return;
 	}
 
+	if (req->request.num_mapped_sgs) {
+		req->request.dma = DMA_ADDR_INVALID;
+		dma_unmap_sg(dwc->dev, req->request.sg,
+				req->request.num_sgs,
+				req->direction ? DMA_TO_DEVICE
+				: DMA_FROM_DEVICE);
+
+		req->request.num_mapped_sgs = 0;
+		return;
+	}
+
 	if (req->mapped) {
 		dma_unmap_single(dwc->dev, req->request.dma,
 				req->request.length, req->direction
@@ -97,7 +124,11 @@ void dwc3_gadget_giveback(struct dwc3_ep *dep, struct dwc3_request *req,
 	struct dwc3			*dwc = dep->dwc;
 
 	if (req->queued) {
-		dep->busy_slot++;
+		if (req->request.num_mapped_sgs)
+			dep->busy_slot += req->request.num_mapped_sgs;
+		else
+			dep->busy_slot++;
+
 		/*
 		 * Skip LINK TRB. We can't use req->trb and check for
 		 * DWC3_TRBCTL_LINK_TRB because it points the TRB we just
@@ -108,6 +139,7 @@ void dwc3_gadget_giveback(struct dwc3_ep *dep, struct dwc3_request *req,
 			dep->busy_slot++;
 	}
 	list_del(&req->list);
+	req->trb = NULL;
 
 	if (req->request.status == -EINPROGRESS)
 		req->request.status = status;
@@ -545,13 +577,20 @@ static void dwc3_gadget_ep_free_request(struct usb_ep *ep,
  * @req: dwc3_request pointer
  */
 static void dwc3_prepare_one_trb(struct dwc3_ep *dep,
-		struct dwc3_request *req, unsigned last)
+		struct dwc3_request *req, dma_addr_t dma,
+		unsigned length, unsigned last, unsigned chain)
 {
+	struct dwc3		*dwc = dep->dwc;
 	struct dwc3_trb_hw	*trb_hw;
 	struct dwc3_trb		trb;
 
 	unsigned int		cur_slot;
 
+	dev_vdbg(dwc->dev, "%s: req %p dma %08llx length %d%s%s\n",
+			dep->name, req, (unsigned long long) dma,
+			length, last ? " last" : "",
+			chain ? " chain" : "");
+
 	trb_hw = &dep->trb_pool[dep->free_slot & DWC3_TRB_MASK];
 	cur_slot = dep->free_slot;
 	dep->free_slot++;
@@ -561,15 +600,18 @@ static void dwc3_prepare_one_trb(struct dwc3_ep *dep,
 			usb_endpoint_xfer_isoc(dep->desc))
 		return;
 
-	dwc3_gadget_move_request_queued(req);
 	memset(&trb, 0, sizeof(trb));
-
-	req->trb = trb_hw;
+	if (!req->trb) {
+		dwc3_gadget_move_request_queued(req);
+		req->trb = trb_hw;
+		req->trb_dma = dwc3_trb_dma_offset(dep, trb_hw);
+	}
 
 	if (usb_endpoint_xfer_isoc(dep->desc)) {
 		trb.isp_imi = true;
 		trb.csp = true;
 	} else {
+		trb.chn = chain;
 		trb.lst = last;
 	}
 
@@ -601,12 +643,11 @@ static void dwc3_prepare_one_trb(struct dwc3_ep *dep,
 		BUG();
 	}
 
-	trb.length	= req->request.length;
-	trb.bplh	= req->request.dma;
+	trb.length	= length;
+	trb.bplh	= dma;
 	trb.hwo		= true;
 
 	dwc3_trb_to_hw(&trb, trb_hw);
-	req->trb_dma = dwc3_trb_dma_offset(dep, trb_hw);
 }
 
 /*
@@ -663,19 +704,58 @@ static void dwc3_prepare_trbs(struct dwc3_ep *dep, bool starting)
 		return;
 
 	list_for_each_entry_safe(req, n, &dep->request_list, list) {
-		trbs_left--;
+		unsigned	length;
+		dma_addr_t	dma;
 
-		if (!trbs_left)
-			last_one = 1;
+		if (req->request.num_mapped_sgs > 0) {
+			struct usb_request *request = &req->request;
+			struct scatterlist *sg = request->sg;
+			struct scatterlist *s;
+			int		i;
 
-		/* Is this the last request? */
-		if (list_empty(&dep->request_list))
-			last_one = 1;
+			for_each_sg(sg, s, request->num_mapped_sgs, i) {
+				unsigned chain = true;
 
-		dwc3_prepare_one_trb(dep, req, last_one);
+				length = sg_dma_len(s);
+				dma = sg_dma_address(s);
 
-		if (last_one)
-			break;
+				if (i == (request->num_mapped_sgs - 1)
+						|| sg_is_last(s)) {
+					last_one = true;
+					chain = false;
+				}
+
+				trbs_left--;
+				if (!trbs_left)
+					last_one = true;
+
+				if (last_one)
+					chain = false;
+
+				dwc3_prepare_one_trb(dep, req, dma, length,
+						last_one, chain);
+
+				if (last_one)
+					break;
+			}
+		} else {
+			dma = req->request.dma;
+			length = req->request.length;
+			trbs_left--;
+
+			if (!trbs_left)
+				last_one = 1;
+
+			/* Is this the last request? */
+			if (list_is_last(&req->list, &dep->request_list))
+				last_one = 1;
+
+			dwc3_prepare_one_trb(dep, req, dma, length,
+					last_one, false);
+
+			if (last_one)
+				break;
+		}
 	}
 }
 
@@ -1989,6 +2069,7 @@ int __devinit dwc3_gadget_init(struct dwc3 *dwc)
 	dwc->gadget.max_speed		= USB_SPEED_SUPER;
 	dwc->gadget.speed		= USB_SPEED_UNKNOWN;
 	dwc->gadget.dev.parent		= dwc->dev;
+	dwc->gadget.sg_supported	= true;
 
 	dma_set_coherent_mask(&dwc->gadget.dev, dwc->dev->coherent_dma_mask);