openwrt-xburst/target/linux/ar7/patches-2.6.24/160-cpmac-rx-ring-use-eoq.diff

--- linux-2.6.24.3/drivers/net/cpmac.c.orig	2008-03-10 23:59:56.000000000 +0000
+++ linux-2.6.24.3/drivers/net/cpmac.c	2008-03-11 00:13:04.000000000 +0000
@@ -187,6 +187,7 @@
 #define CPMAC_EOQ			0x1000
 	struct sk_buff *skb;
 	struct cpmac_desc *next;
+	struct cpmac_desc *prev;
 	dma_addr_t mapping;
 	dma_addr_t data_mapping;
 };
@@ -242,6 +243,16 @@
 	printk("\n");
 }
 
+static void cpmac_dump_all_desc(struct net_device *dev)
+{
+        struct cpmac_priv *priv = netdev_priv(dev);
+        struct cpmac_desc *dump = priv->rx_head;
+        do {
+                cpmac_dump_desc(dev, dump);
+                dump = dump->next;
+        } while (dump != priv->rx_head);
+}
+
 static void cpmac_dump_skb(struct net_device *dev, struct sk_buff *skb)
 {
 	int i;
@@ -413,21 +424,40 @@
 static int cpmac_poll(struct napi_struct *napi, int budget)
 {
 	struct sk_buff *skb;
-	struct cpmac_desc *desc;
-	int received = 0;
+	struct cpmac_desc *desc, *restart;
 	struct cpmac_priv *priv = container_of(napi, struct cpmac_priv, napi);
+	int received = 0, processed = 0;
 
 	spin_lock(&priv->rx_lock);
 	if (unlikely(!priv->rx_head)) {
 		if (netif_msg_rx_err(priv) && net_ratelimit())
 			printk(KERN_WARNING "%s: rx: polling, but no queue\n",
 			       priv->dev->name);
+		spin_unlock(&priv->rx_lock);
 		netif_rx_complete(priv->dev, napi);
 		return 0;
 	}
 
 	desc = priv->rx_head;
+	restart = NULL;
 	while (((desc->dataflags & CPMAC_OWN) == 0) && (received < budget)) {
+		processed++;
+		
+		if ((desc->dataflags & CPMAC_EOQ) != 0) {
+			/* The last update to eoq->hw_next didn't happen soon enough, and the
+			* receiver stopped here. Remember this descriptor so we can restart
+			* the receiver after freeing some space.
+			*/
+			if (unlikely(restart)) {
+				if (netif_msg_rx_err(priv))
+					printk(KERN_ERR "%s: poll found a duplicate EOQ: %p and %p\n",
+						priv->dev->name, restart, desc);
+				goto fatal_error;
+			}
+			
+			restart = desc->next;
+		}
+
 		skb = cpmac_rx_one(priv, desc);
 		if (likely(skb)) {
 			netif_receive_skb(skb);
@@ -436,19 +466,81 @@
 		desc = desc->next;
 	}
 
+	if (desc != priv->rx_head) {
+		/* We freed some buffers, but not the whole ring, add what we did free to the rx list */ 
+		desc->prev->hw_next = (u32)0;
+		priv->rx_head->prev->hw_next = priv->rx_head->mapping;
+	}
+
+	/* Optimization: If we did not actually process an EOQ (perhaps because of 
+	* quota limits), check to see if the tail of the queue has EOQ set. We
+	* should immediately restart in that case so that the receiver can restart
+	* and run in parallel with more packet processing. This lets us handle slightly
+	* larger bursts before running out of ring space (assuming dev->weight < ring_size)
+	*/
+	if (!restart &&
+	     (priv->rx_head->prev->dataflags & (CPMAC_OWN|CPMAC_EOQ)) == CPMAC_EOQ &&
+	     (priv->rx_head->dataflags & CPMAC_OWN) != 0) {
+		/* reset EOQ so the poll loop (above) doesn't try to restart this when it
+		* eventually gets to this descriptor.
+		*/
+		priv->rx_head->prev->dataflags &= ~CPMAC_EOQ;
+		restart = priv->rx_head;
+	}
+
+	if (restart) {
+		priv->dev->stats.rx_errors++;
+		priv->dev->stats.rx_fifo_errors++;
+		if (netif_msg_rx_err(priv) && net_ratelimit())
+			printk(KERN_WARNING "%s: rx dma ring overrun\n", priv->dev->name);
+
+		if (unlikely((restart->dataflags & CPMAC_OWN) == 0)) {
+			if (netif_msg_drv(priv))
+				printk(KERN_ERR "%s: cpmac_poll is trying to restart rx from a descriptor that's not free: %p\n",
+					priv->dev->name, restart);
+				goto fatal_error;
+		}
+
+		cpmac_write(priv->regs, CPMAC_RX_PTR(0), restart->mapping);
+	}
+
 	priv->rx_head = desc;
 	spin_unlock(&priv->rx_lock);
 	if (unlikely(netif_msg_rx_status(priv)))
 		printk(KERN_DEBUG "%s: poll processed %d packets\n",
 		       priv->dev->name, received);
-	if (desc->dataflags & CPMAC_OWN) {
+	if (processed == 0) {
+		/* we ran out of packets to read, revert to interrupt-driven mode */ 
 		netif_rx_complete(priv->dev, napi);
-		cpmac_write(priv->regs, CPMAC_RX_PTR(0), (u32)desc->mapping);
 		cpmac_write(priv->regs, CPMAC_RX_INT_ENABLE, 1);
 		return 0;
 	}
 
 	return 1;
+
+fatal_error:
+	/* Something went horribly wrong. Reset hardware to try to recover rather than wedging. */ 
+	
+	if (netif_msg_drv(priv)) {
+		printk(KERN_ERR "%s: cpmac_poll is confused. Resetting hardware\n", priv->dev->name);
+		cpmac_dump_all_desc(priv->dev);
+		printk(KERN_DEBUG "%s: RX_PTR(0)=0x%08x RX_ACK(0)=0x%08x\n",
+			priv->dev->name,
+			cpmac_read(priv->regs, CPMAC_RX_PTR(0)),
+			cpmac_read(priv->regs, CPMAC_RX_ACK(0)));
+	}
+
+	spin_unlock(&priv->rx_lock);
+	netif_rx_complete(priv->dev, napi);
+	netif_stop_queue(priv->dev);
+	napi_disable(&priv->napi);
+	
+	atomic_inc(&priv->reset_pending);
+	cpmac_hw_stop(priv->dev);
+	if (!schedule_work(&priv->reset_work))
+		atomic_dec(&priv->reset_pending);
+	return 0;
+ 
 }
 
 static int cpmac_start_xmit(struct sk_buff *skb, struct net_device *dev)
@@ -625,8 +717,10 @@
 			desc->dataflags = CPMAC_OWN;
 			dev->stats.rx_dropped++;
 		}
+		desc->hw_next = desc->next->mapping;
 		desc = desc->next;
 	}
+	priv->rx_head->prev->hw_next = 0;
 }
 
 static void cpmac_clear_tx(struct net_device *dev)
@@ -927,9 +1021,12 @@
 		desc->buflen = CPMAC_SKB_SIZE;
 		desc->dataflags = CPMAC_OWN;
 		desc->next = &priv->rx_head[(i + 1) % priv->ring_size];
+		desc->next->prev = desc;
 		desc->hw_next = (u32)desc->next->mapping;
 	}
 
+	priv->rx_head->prev->hw_next = (u32)0;
+
 	if ((res = request_irq(dev->irq, cpmac_irq, IRQF_SHARED,
 			       dev->name, dev))) {
 		if (netif_msg_drv(priv))