usb: gadget: u_ether: move hardware transmit to RX NAPI

In order to reduce the interrupt times in the embedded system,
a receiving workqueue is introduced.
This modification also enhanced the overall throughput as the
benefits of reducing interrupt occurrence.

This work was derived from previous work:
u_ether: move hardware transmit to RX workqueue.
Which should be base on codeaurora's work.

However, the benchmark on my platform shows the throughput
with workqueue is slightly better than NAPI.
Signed-off-by: Weinn Jheng <clanlab.proj@gmail.com>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Cc: David S. Miller <davem@davemloft.net>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Manu Gautam <mgautam@codeaurora.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/u_ether.c

@@ -48,6 +48,8 @@
 
 #define UETH__VERSION	"29-May-2008"
 
+#define GETHER_NAPI_WEIGHT	32
+
 struct eth_dev {
 	/* lock is held while accessing port_usb
 	 */
@@ -72,6 +74,7 @@ struct eth_dev {
 						struct sk_buff_head *list);
 
 	struct work_struct	work;
+	struct napi_struct	rx_napi;
 
 	unsigned long		todo;
 #define	WORK_RX_MEMORY		0
@@ -253,18 +256,16 @@ rx_submit(struct eth_dev *dev, struct usb_request *req, gfp_t gfp_flags)
 		DBG(dev, "rx submit --> %d\n", retval);
 		if (skb)
 			dev_kfree_skb_any(skb);
-		spin_lock_irqsave(&dev->req_lock, flags);
-		list_add(&req->list, &dev->rx_reqs);
-		spin_unlock_irqrestore(&dev->req_lock, flags);
 	}
 	return retval;
 }
 
 static void rx_complete(struct usb_ep *ep, struct usb_request *req)
 {
-	struct sk_buff	*skb = req->context, *skb2;
+	struct sk_buff	*skb = req->context;
 	struct eth_dev	*dev = ep->driver_data;
 	int		status = req->status;
+	bool		rx_queue = 0;
 
 	switch (status) {
 
@@ -288,30 +289,8 @@ static void rx_complete(struct usb_ep *ep, struct usb_request *req)
 		} else {
 			skb_queue_tail(&dev->rx_frames, skb);
 		}
-		skb = NULL;
-
-		skb2 = skb_dequeue(&dev->rx_frames);
-		while (skb2) {
-			if (status < 0
-					|| ETH_HLEN > skb2->len
-					|| skb2->len > VLAN_ETH_FRAME_LEN) {
-				dev->net->stats.rx_errors++;
-				dev->net->stats.rx_length_errors++;
-				DBG(dev, "rx length %d\n", skb2->len);
-				dev_kfree_skb_any(skb2);
-				goto next_frame;
-			}
-			skb2->protocol = eth_type_trans(skb2, dev->net);
-			dev->net->stats.rx_packets++;
-			dev->net->stats.rx_bytes += skb2->len;
-
-			/* no buffer copies needed, unless hardware can't
-			 * use skb buffers.
-			 */
-			status = netif_rx(skb2);
-next_frame:
-			skb2 = skb_dequeue(&dev->rx_frames);
-		}
+		if (!status)
+			rx_queue = 1;
 		break;
 
 	/* software-driven interface shutdown */
@@ -334,22 +313,20 @@ static void rx_complete(struct usb_ep *ep, struct usb_request *req)
 		/* FALLTHROUGH */
 
 	default:
+		rx_queue = 1;
+		dev_kfree_skb_any(skb);
 		dev->net->stats.rx_errors++;
 		DBG(dev, "rx status %d\n", status);
 		break;
 	}
 
-	if (skb)
-		dev_kfree_skb_any(skb);
-	if (!netif_running(dev->net)) {
 clean:
 		spin_lock(&dev->req_lock);
 		list_add(&req->list, &dev->rx_reqs);
 		spin_unlock(&dev->req_lock);
-		req = NULL;
-	}
-	if (req)
-		rx_submit(dev, req, GFP_ATOMIC);
+
+	if (rx_queue && likely(napi_schedule_prep(&dev->rx_napi)))
+		__napi_schedule(&dev->rx_napi);
 }
 
 static int prealloc(struct list_head *list, struct usb_ep *ep, unsigned n)
@@ -414,16 +391,24 @@ static void rx_fill(struct eth_dev *dev, gfp_t gfp_flags)
 {
 	struct usb_request	*req;
 	unsigned long		flags;
+	int			rx_counts = 0;
 
 	/* fill unused rxq slots with some skb */
 	spin_lock_irqsave(&dev->req_lock, flags);
 	while (!list_empty(&dev->rx_reqs)) {
+
+		if (++rx_counts > qlen(dev->gadget, dev->qmult))
+			break;
+
 		req = container_of(dev->rx_reqs.next,
 				struct usb_request, list);
 		list_del_init(&req->list);
 		spin_unlock_irqrestore(&dev->req_lock, flags);
 
 		if (rx_submit(dev, req, gfp_flags) < 0) {
+			spin_lock_irqsave(&dev->req_lock, flags);
+			list_add(&req->list, &dev->rx_reqs);
+			spin_unlock_irqrestore(&dev->req_lock, flags);
 			defer_kevent(dev, WORK_RX_MEMORY);
 			return;
 		}
@@ -433,6 +418,41 @@ static void rx_fill(struct eth_dev *dev, gfp_t gfp_flags)
 	spin_unlock_irqrestore(&dev->req_lock, flags);
 }
 
+static int gether_poll(struct napi_struct *napi, int budget)
+{
+	struct eth_dev  *dev = container_of(napi, struct eth_dev, rx_napi);
+	struct sk_buff	*skb;
+	unsigned int	work_done = 0;
+	int		status = 0;
+
+	while ((skb = skb_dequeue(&dev->rx_frames))) {
+		if (status < 0
+				|| ETH_HLEN > skb->len
+				|| skb->len > VLAN_ETH_FRAME_LEN) {
+			dev->net->stats.rx_errors++;
+			dev->net->stats.rx_length_errors++;
+			DBG(dev, "rx length %d\n", skb->len);
+			dev_kfree_skb_any(skb);
+			continue;
+		}
+		skb->protocol = eth_type_trans(skb, dev->net);
+		dev->net->stats.rx_packets++;
+		dev->net->stats.rx_bytes += skb->len;
+
+		status = netif_rx_ni(skb);
+	}
+
+	if (netif_running(dev->net)) {
+		rx_fill(dev, GFP_KERNEL);
+		work_done++;
+	}
+
+	if (work_done < budget)
+		napi_complete(&dev->rx_napi);
+
+	return work_done;
+}
+
 static void eth_work(struct work_struct *work)
 {
 	struct eth_dev	*dev = container_of(work, struct eth_dev, work);
@@ -625,6 +645,7 @@ static void eth_start(struct eth_dev *dev, gfp_t gfp_flags)
 	/* and open the tx floodgates */
 	atomic_set(&dev->tx_qlen, 0);
 	netif_wake_queue(dev->net);
+	napi_enable(&dev->rx_napi);
 }
 
 static int eth_open(struct net_device *net)
@@ -651,6 +672,7 @@ static int eth_stop(struct net_device *net)
 	unsigned long	flags;
 
 	VDBG(dev, "%s\n", __func__);
+	napi_disable(&dev->rx_napi);
 	netif_stop_queue(net);
 
 	DBG(dev, "stop stats: rx/tx %ld/%ld, errs %ld/%ld\n",
@@ -768,6 +790,7 @@ struct eth_dev *gether_setup_name(struct usb_gadget *g,
 		return ERR_PTR(-ENOMEM);
 
 	dev = netdev_priv(net);
+	netif_napi_add(net, &dev->rx_napi, gether_poll, GETHER_NAPI_WEIGHT);
 	spin_lock_init(&dev->lock);
 	spin_lock_init(&dev->req_lock);
 	INIT_WORK(&dev->work, eth_work);
@@ -830,6 +853,7 @@ struct net_device *gether_setup_name_default(const char *netname)
 		return ERR_PTR(-ENOMEM);
 
 	dev = netdev_priv(net);
+	netif_napi_add(net, &dev->rx_napi, gether_poll, GETHER_NAPI_WEIGHT);
 	spin_lock_init(&dev->lock);
 	spin_lock_init(&dev->req_lock);
 	INIT_WORK(&dev->work, eth_work);
@@ -1113,6 +1137,7 @@ void gether_disconnect(struct gether *link)
 {
 	struct eth_dev		*dev = link->ioport;
 	struct usb_request	*req;
+	struct sk_buff		*skb;
 
 	WARN_ON(!dev);
 	if (!dev)
@@ -1139,6 +1164,12 @@ void gether_disconnect(struct gether *link)
 		spin_lock(&dev->req_lock);
 	}
 	spin_unlock(&dev->req_lock);
+
+	spin_lock(&dev->rx_frames.lock);
+	while ((skb = __skb_dequeue(&dev->rx_frames)))
+		dev_kfree_skb_any(skb);
+	spin_unlock(&dev->rx_frames.lock);
+
 	link->in_ep->driver_data = NULL;
 	link->in_ep->desc = NULL;