From 8988d03a8e07e94a07df6707828763b767fe6f0e Mon Sep 17 00:00:00 2001
From: Matteo Croce <rootkit85@yahoo.it>
Date: Tue, 11 Mar 2008 00:59:11 +0000
Subject: [PATCH] cpmac: patch to reimplement rx ring with EOQ markers to avoid
reset storms (closes #2569)
SVN-Revision: 10585
---
.../160-cpmac-rx-ring-use-eoq.diff | 178 ++++++++++++++++++
1 file changed, 178 insertions(+)
create mode 100644 target/linux/ar7/patches-2.6.24/160-cpmac-rx-ring-use-eoq.diff
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
index 0000000000..47f7e6c989
--- /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))
--
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