ENGR00172303 - FEC : fix 'eth0: tx queue full!' issue.

The issue is hard to reproduce in normal envrionment. And
the reproduce rate is about 40% when doing VTE auto test.

while the driver did report being busy when the link is down
or no transmission buffers are available, it did not stop the
queue, causing instant retries. furthermore, transmission being
triggered with link down was caused by unconditional queue
wakes, especially on timeouts.

Now, wake queue only if link is up and transmission buffers
are available, and dont forget to wake queue when link has
been adjusted. next, add stop queue notification upon driver
induced transmission problems, so network stack has a chance
to handle the situation.

Signed-off-by: Fugang Duan  <B38611@freescale.com>

diff --git a/drivers/net/fec.c b/drivers/net/fec.c
index 872b7c4c5cc62eb79f1f835c9d5dbedb0a171295..2078ef8d25f0a1ea592c090aa2e2539464991499 100755 (executable)
--- a/drivers/net/fec.c
+++ b/drivers/net/fec.c
@@ -276,12 +276,14 @@ fec_enet_start_xmit(struct sk_buff *skb, struct net_device *ndev)
        unsigned long   estatus;
        unsigned long flags;
 
+       spin_lock_irqsave(&fep->hw_lock, flags);
        if (!fep->link) {
                /* Link is down or autonegotiation is in progress. */
+               netif_stop_queue(ndev);
+               spin_unlock_irqrestore(&fep->hw_lock, flags);
                return NETDEV_TX_BUSY;
        }
 
-       spin_lock_irqsave(&fep->hw_lock, flags);
        /* Fill in a Tx ring entry */
        bdp = fep->cur_tx;
 
@@ -292,6 +294,7 @@ fec_enet_start_xmit(struct sk_buff *skb, struct net_device *ndev)
                 * This should not happen, since ndev->tbusy should be set.
                 */
                printk("%s: tx queue full!.\n", ndev->name);
+               netif_stop_queue(ndev);
                spin_unlock_irqrestore(&fep->hw_lock, flags);
                return NETDEV_TX_BUSY;
        }
@@ -311,8 +314,8 @@ fec_enet_start_xmit(struct sk_buff *skb, struct net_device *ndev)
        if (((unsigned long) bufaddr) & FEC_ALIGNMENT) {
                unsigned int index;
                index = bdp - fep->tx_bd_base;
-               memcpy(fep->tx_bounce[index], (void *)skb->data, skb->len);
-               bufaddr = fep->tx_bounce[index];
+               bufaddr = PTR_ALIGN(fep->tx_bounce[index], FEC_ALIGNMENT + 1);
+               memcpy(bufaddr, (void *)skb->data, skb->len);
        }
 
        if (fep->ptimer_present) {
@@ -382,7 +385,8 @@ fec_timeout(struct net_device *ndev)
        ndev->stats.tx_errors++;
 
        fec_restart(ndev, fep->full_duplex);
-       netif_wake_queue(ndev);
+       if (fep->link && !fep->tx_full)
+               netif_wake_queue(ndev);
 }
 
 static void
@@ -409,6 +413,8 @@ fec_enet_tx(struct net_device *ndev)
                bdp->cbd_bufaddr = 0;
 
                skb = fep->tx_skbuff[fep->skb_dirty];
+               if (!skb)
+                       break;
                /* Check for errors. */
                if (status & (BD_ENET_TX_HB | BD_ENET_TX_LC |
                                   BD_ENET_TX_RL | BD_ENET_TX_UN |
@@ -730,9 +736,11 @@ static void fec_enet_adjust_link(struct net_device *ndev)
        /* Link on or off change */
        if (phy_dev->link != fep->link) {
                fep->link = phy_dev->link;
-               if (phy_dev->link)
+               if (phy_dev->link) {
                        fec_restart(ndev, phy_dev->duplex);
-               else
+                       if (!fep->tx_full)
+                               netif_wake_queue(ndev);
+               } else
                        fec_stop(ndev);
                status_change = 1;
        }
@@ -1071,6 +1079,10 @@ static int fec_enet_alloc_buffers(struct net_device *ndev)
        bdp = fep->tx_bd_base;
        for (i = 0; i < TX_RING_SIZE; i++) {
                fep->tx_bounce[i] = kmalloc(FEC_ENET_TX_FRSIZE, GFP_KERNEL);
+               if (!fep->tx_bounce[i]) {
+                       fec_enet_free_buffers(ndev);
+                       return -ENOMEM;
+               }
 
                bdp->cbd_sc = 0;
                bdp->cbd_bufaddr = 0;