[TG3]: Fix 4GB boundary tx handling

Fix and simplify the workaround code for the 4GB boundary tx buffer
hardware bug.

1. Need to unmap the original SKB's dma addresses if a new SKB cannot
   be allocated.

2. Need to pass the base flag to tigon3_4gb_hwbug_workaround() or TSO
   won't work properly.

3. The guilty entry and length parameters for
   tigon3_4gb_hwbug_workaround() are removed as they are not necessary.

4. Remove assumption that only one fragment can hit the 4GB boundary.
   Another fragment can hit 8GB for example.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 39 insertions, 55 deletions

diff --git a/drivers/net/tg3.c b/drivers/net/tg3.c
index 06b02c59d90b..81f4aedf534c 100644
--- a/drivers/net/tg3.c
+++ b/drivers/net/tg3.c
@@ -3442,31 +3442,47 @@ static void tg3_tx_timeout(struct net_device *dev)
         schedule_work(&tp->reset_task);
 }
 
+/* Test for DMA buffers crossing any 4GB boundaries: 4G, 8G, etc */
+static inline int tg3_4g_overflow_test(dma_addr_t mapping, int len)
+{
+        u32 base = (u32) mapping & 0xffffffff;
+
+        return ((base > 0xffffdcc0) &&
+                (base + len + 8 < base));
+}
+
 static void tg3_set_txd(struct tg3 *, int, dma_addr_t, int, u32, u32);
 
 static int tigon3_4gb_hwbug_workaround(struct tg3 *tp, struct sk_buff *skb,
-                                       u32 guilty_entry, int guilty_len,
-                                       u32 last_plus_one, u32 *start, u32 mss)
+                                       u32 last_plus_one, u32 *start,
+                                       u32 base_flags, u32 mss)
 {
         struct sk_buff *new_skb = skb_copy(skb, GFP_ATOMIC);
-        dma_addr_t new_addr;
+        dma_addr_t new_addr = 0;
         u32 entry = *start;
-        int i;
+        int i, ret = 0;
 
         if (!new_skb) {
-                dev_kfree_skb(skb);
-                return -1;
+                ret = -1;
+        } else {
+                /* New SKB is guaranteed to be linear. */
+                entry = *start;
+                new_addr = pci_map_single(tp->pdev, new_skb->data, new_skb->len,
+                                          PCI_DMA_TODEVICE);
+                /* Make sure new skb does not cross any 4G boundaries.
+                 * Drop the packet if it does.
+                 */
+                if (tg3_4g_overflow_test(new_addr, new_skb->len)) {
+                        ret = -1;
+                        dev_kfree_skb(new_skb);
+                        new_skb = NULL;
+                } else {
+                        tg3_set_txd(tp, entry, new_addr, new_skb->len,
+                                    base_flags, 1 | (mss << 1));
+                        *start = NEXT_TX(entry);
+                }
         }
 
-        /* New SKB is guaranteed to be linear. */
-        entry = *start;
-        new_addr = pci_map_single(tp->pdev, new_skb->data, new_skb->len,
-                                  PCI_DMA_TODEVICE);
-        tg3_set_txd(tp, entry, new_addr, new_skb->len,
-                    (skb->ip_summed == CHECKSUM_HW) ?
-                    TXD_FLAG_TCPUDP_CSUM : 0, 1 | (mss << 1));
-        *start = NEXT_TX(entry);
-
         /* Now clean up the sw ring entries. */
         i = 0;
         while (entry != last_plus_one) {
@@ -3491,7 +3507,7 @@ static int tigon3_4gb_hwbug_workaround(struct tg3 *tp, struct sk_buff *skb,
 
         dev_kfree_skb(skb);
 
-        return 0;
+        return ret;
 }
 
 static void tg3_set_txd(struct tg3 *tp, int entry,
@@ -3517,19 +3533,10 @@ static void tg3_set_txd(struct tg3 *tp, int entry,
         txd->vlan_tag = vlan_tag << TXD_VLAN_TAG_SHIFT;
 }
 
-static inline int tg3_4g_overflow_test(dma_addr_t mapping, int len)
-{
-        u32 base = (u32) mapping & 0xffffffff;
-
-        return ((base > 0xffffdcc0) &&
-                (base + len + 8 < base));
-}
-
 static int tg3_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
         struct tg3 *tp = netdev_priv(dev);
         dma_addr_t mapping;
-        unsigned int i;
         u32 len, entry, base_flags, mss;
         int would_hit_hwbug;
 
@@ -3624,7 +3631,7 @@ static int tg3_start_xmit(struct sk_buff *skb, struct net_device *dev)
         would_hit_hwbug = 0;
 
         if (tg3_4g_overflow_test(mapping, len))
-                would_hit_hwbug = entry + 1;
+                would_hit_hwbug = 1;
 
         tg3_set_txd(tp, entry, mapping, len, base_flags,
                     (skb_shinfo(skb)->nr_frags == 0) | (mss << 1));
@@ -3648,12 +3655,8 @@ static int tg3_start_xmit(struct sk_buff *skb, struct net_device *dev)
                         tp->tx_buffers[entry].skb = NULL;
                         pci_unmap_addr_set(&tp->tx_buffers[entry], mapping, mapping);
 
-                        if (tg3_4g_overflow_test(mapping, len)) {
-                                /* Only one should match. */
-                                if (would_hit_hwbug)
-                                        BUG();
-                                would_hit_hwbug = entry + 1;
-                        }
+                        if (tg3_4g_overflow_test(mapping, len))
+                                would_hit_hwbug = 1;
 
                         if (tp->tg3_flags2 & TG3_FLG2_HW_TSO)
                                 tg3_set_txd(tp, entry, mapping, len,
@@ -3669,34 +3672,15 @@ static int tg3_start_xmit(struct sk_buff *skb, struct net_device *dev)
         if (would_hit_hwbug) {
                 u32 last_plus_one = entry;
                 u32 start;
-                unsigned int len = 0;
-
-                would_hit_hwbug -= 1;
-                entry = entry - 1 - skb_shinfo(skb)->nr_frags;
-                entry &= (TG3_TX_RING_SIZE - 1);
-                start = entry;
-                i = 0;
-                while (entry != last_plus_one) {
-                        if (i == 0)
-                                len = skb_headlen(skb);
-                        else
-                                len = skb_shinfo(skb)->frags[i-1].size;
-
-                        if (entry == would_hit_hwbug)
-                                break;
 
-                        i++;
-                        entry = NEXT_TX(entry);
-
-                }
+                start = entry - 1 - skb_shinfo(skb)->nr_frags;
+                start &= (TG3_TX_RING_SIZE - 1);
 
                 /* If the workaround fails due to memory/mapping
                  * failure, silently drop this packet.
                  */
-                if (tigon3_4gb_hwbug_workaround(tp, skb,
-                                                entry, len,
-                                                last_plus_one,
-                                                &start, mss))
+                if (tigon3_4gb_hwbug_workaround(tp, skb, last_plus_one,
+                                                &start, base_flags, mss))
                         goto out_unlock;
 
                 entry = start;