usb: dwc2: gadget: Add scatter-gather mode

This patch adds support for transferring requests, which are
non-contiguous in physical memory, i.e. the data buffer is described by
a scatter-list. This allows transferring large requests without relying
on error-prone contiguous buffer allocations. This way of allocating
requests is already implemented in functionfs and TCM USB functions and
automatically used if UDC driver advertises scatter-gather suppport.
Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
[mszyprow: fixed null pointer issue, rewrote commit message]
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc2/gadget.c

@@ -768,22 +768,13 @@ static u32 dwc2_gadget_get_desc_params(struct dwc2_hsotg_ep *hs_ep, u32 *mask)
 	return desc_size;
 }
 
-/*
- * dwc2_gadget_config_nonisoc_xfer_ddma - prepare non ISOC DMA desc chain.
- * @hs_ep: The endpoint
- * @dma_buff: DMA address to use
- * @len: Length of the transfer
- *
- * This function will iterate over descriptor chain and fill its entries
- * with corresponding information based on transfer data.
- */
-static void dwc2_gadget_config_nonisoc_xfer_ddma(struct dwc2_hsotg_ep *hs_ep,
+static void dwc2_gadget_fill_nonisoc_xfer_ddma_one(struct dwc2_hsotg_ep *hs_ep,
+						 struct dwc2_dma_desc **desc,
 						 dma_addr_t dma_buff,
-						 unsigned int len)
+						 unsigned int len,
+						 bool true_last)
 {
-	struct dwc2_hsotg *hsotg = hs_ep->parent;
 	int dir_in = hs_ep->dir_in;
-	struct dwc2_dma_desc *desc = hs_ep->desc_list;
 	u32 mps = hs_ep->ep.maxpacket;
 	u32 maxsize = 0;
 	u32 offset = 0;
@@ -798,39 +789,77 @@ static void dwc2_gadget_config_nonisoc_xfer_ddma(struct dwc2_hsotg_ep *hs_ep,
 		hs_ep->desc_count = 1;
 
 	for (i = 0; i < hs_ep->desc_count; ++i) {
-		desc->status = 0;
-		desc->status |= (DEV_DMA_BUFF_STS_HBUSY
+		(*desc)->status = 0;
+		(*desc)->status |= (DEV_DMA_BUFF_STS_HBUSY
 				 << DEV_DMA_BUFF_STS_SHIFT);
 
 		if (len > maxsize) {
 			if (!hs_ep->index && !dir_in)
-				desc->status |= (DEV_DMA_L | DEV_DMA_IOC);
+				(*desc)->status |= (DEV_DMA_L | DEV_DMA_IOC);
 
-			desc->status |= (maxsize <<
-						DEV_DMA_NBYTES_SHIFT & mask);
-			desc->buf = dma_buff + offset;
+			(*desc)->status |=
+				maxsize << DEV_DMA_NBYTES_SHIFT & mask;
+			(*desc)->buf = dma_buff + offset;
 
 			len -= maxsize;
 			offset += maxsize;
 		} else {
-			desc->status |= (DEV_DMA_L | DEV_DMA_IOC);
+			if (true_last)
+				(*desc)->status |= (DEV_DMA_L | DEV_DMA_IOC);
 
 			if (dir_in)
-				desc->status |= (len % mps) ? DEV_DMA_SHORT :
-					((hs_ep->send_zlp) ? DEV_DMA_SHORT : 0);
-			if (len > maxsize)
-				dev_err(hsotg->dev, "wrong len %d\n", len);
+				(*desc)->status |= (len % mps) ? DEV_DMA_SHORT :
+					((hs_ep->send_zlp && true_last) ?
+					DEV_DMA_SHORT : 0);
 
-			desc->status |=
+			(*desc)->status |=
 				len << DEV_DMA_NBYTES_SHIFT & mask;
-			desc->buf = dma_buff + offset;
+			(*desc)->buf = dma_buff + offset;
 		}
 
-		desc->status &= ~DEV_DMA_BUFF_STS_MASK;
-		desc->status |= (DEV_DMA_BUFF_STS_HREADY
+		(*desc)->status &= ~DEV_DMA_BUFF_STS_MASK;
+		(*desc)->status |= (DEV_DMA_BUFF_STS_HREADY
 				 << DEV_DMA_BUFF_STS_SHIFT);
-		desc++;
+		(*desc)++;
+	}
+}
+
+/*
+ * dwc2_gadget_config_nonisoc_xfer_ddma - prepare non ISOC DMA desc chain.
+ * @hs_ep: The endpoint
+ * @ureq: Request to transfer
+ * @offset: offset in bytes
+ * @len: Length of the transfer
+ *
+ * This function will iterate over descriptor chain and fill its entries
+ * with corresponding information based on transfer data.
+ */
+static void dwc2_gadget_config_nonisoc_xfer_ddma(struct dwc2_hsotg_ep *hs_ep,
+						 struct usb_request *ureq,
+						 unsigned int offset,
+						 unsigned int len)
+{
+	struct dwc2_dma_desc *desc = hs_ep->desc_list;
+	struct scatterlist *sg;
+	int i;
+	u8 desc_count = 0;
+
+	/* non-DMA sg buffer */
+	if (!ureq->num_sgs) {
+		dwc2_gadget_fill_nonisoc_xfer_ddma_one(hs_ep, &desc,
+			ureq->dma + offset, len, true);
+		return;
 	}
+
+	/* DMA sg buffer */
+	for_each_sg(ureq->sg, sg, ureq->num_sgs, i) {
+		dwc2_gadget_fill_nonisoc_xfer_ddma_one(hs_ep, &desc,
+			sg_dma_address(sg) + sg->offset, sg_dma_len(sg),
+			sg_is_last(sg));
+		desc_count += hs_ep->desc_count;
+	}
+
+	hs_ep->desc_count = desc_count;
 }
 
 /*
@@ -944,7 +973,13 @@ static void dwc2_gadget_start_isoc_ddma(struct dwc2_hsotg_ep *hs_ep)
 
 	hs_ep->next_desc = 0;
 	list_for_each_entry_safe(hs_req, treq, &hs_ep->queue, queue) {
-		ret = dwc2_gadget_fill_isoc_desc(hs_ep, hs_req->req.dma,
+		dma_addr_t dma_addr = hs_req->req.dma;
+
+		if (hs_req->req.num_sgs) {
+			WARN_ON(hs_req->req.num_sgs > 1);
+			dma_addr = sg_dma_address(hs_req->req.sg);
+		}
+		ret = dwc2_gadget_fill_isoc_desc(hs_ep, dma_addr,
 						 hs_req->req.length);
 		if (ret)
 			break;
@@ -1100,7 +1135,7 @@ static void dwc2_hsotg_start_req(struct dwc2_hsotg *hsotg,
 			offset = ureq->actual;
 
 		/* Fill DDMA chain entries */
-		dwc2_gadget_config_nonisoc_xfer_ddma(hs_ep, ureq->dma + offset,
+		dwc2_gadget_config_nonisoc_xfer_ddma(hs_ep, ureq, offset,
 						     length);
 
 		/* write descriptor chain address to control register */
@@ -1399,7 +1434,13 @@ static int dwc2_hsotg_ep_queue(struct usb_ep *ep, struct usb_request *req,
 	 */
 	if (using_desc_dma(hs) && hs_ep->isochronous) {
 		if (hs_ep->target_frame != TARGET_FRAME_INITIAL) {
-			dwc2_gadget_fill_isoc_desc(hs_ep, hs_req->req.dma,
+			dma_addr_t dma_addr = hs_req->req.dma;
+
+			if (hs_req->req.num_sgs) {
+				WARN_ON(hs_req->req.num_sgs > 1);
+				dma_addr = sg_dma_address(hs_req->req.sg);
+			}
+			dwc2_gadget_fill_isoc_desc(hs_ep, dma_addr,
 						   hs_req->req.length);
 		}
 		return 0;
@@ -1987,13 +2028,12 @@ static void dwc2_hsotg_program_zlp(struct dwc2_hsotg *hsotg,
 		dev_dbg(hsotg->dev, "Receiving zero-length packet on ep%d\n",
 			index);
 	if (using_desc_dma(hsotg)) {
-		/* Not specific buffer needed for ep0 ZLP */
-		dma_addr_t dma = hs_ep->desc_list_dma;
-
 		if (!index)
 			dwc2_gadget_set_ep0_desc_chain(hsotg, hs_ep);
 
-		dwc2_gadget_config_nonisoc_xfer_ddma(hs_ep, dma, 0);
+		/* Not specific buffer needed for ep0 ZLP */
+		dwc2_gadget_fill_nonisoc_xfer_ddma_one(hs_ep, &hs_ep->desc_list,
+			hs_ep->desc_list_dma, 0, true);
 	} else {
 		dwc2_writel(hsotg, DXEPTSIZ_MC(1) | DXEPTSIZ_PKTCNT(1) |
 			    DXEPTSIZ_XFERSIZE(0),
@@ -4386,6 +4426,7 @@ static int dwc2_hsotg_udc_start(struct usb_gadget *gadget,
 	hsotg->enabled = 0;
 	spin_unlock_irqrestore(&hsotg->lock, flags);
 
+	gadget->sg_supported = using_desc_dma(hsotg);
 	dev_info(hsotg->dev, "bound driver %s\n", driver->driver.name);
 
 	return 0;