cpmac: patch to reimplement rx ring with EOQ markers to avoid reset storms (closes...

SVN-Revision: 10585

diff --git a/target/linux/ar7/patches-2.6.24/160-cpmac-rx-ring-use-eoq.diff b/target/linux/ar7/patches-2.6.24/160-cpmac-rx-ring-use-eoq.diff
new file mode 100644 (file)
index 0000000..47f7e6c
--- /dev/null
+++ b/target/linux/ar7/patches-2.6.24/160-cpmac-rx-ring-use-eoq.diff
@@ -0,0 +1,178 @@
+--- 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))