tg3: Fix 5906 transmit hangs

The 5906 has trouble with fragments that are less than 8 bytes in size.
This patch works around the problem by pivoting the 5906's transmit
routine to tg3_start_xmit_dma_bug() and introducing a new SHORT_DMA_BUG
flag that enables code to detect and react to the problematic condition.

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

2 files changed, 20 insertions, 7 deletions

diff --git a/drivers/net/tg3.c b/drivers/net/tg3.c
index da808250c866..a7a582e37469 100644
--- a/drivers/net/tg3.c
+++ b/drivers/net/tg3.c
@@ -5393,7 +5393,7 @@ static netdev_tx_t tg3_start_xmit_dma_bug(struct sk_buff *skb,
         mss = 0;
         if ((mss = skb_shinfo(skb)->gso_size) != 0) {
                 struct iphdr *iph;
-                int tcp_opt_len, ip_tcp_len, hdr_len;
+                u32 tcp_opt_len, ip_tcp_len, hdr_len;
 
                 if (skb_header_cloned(skb) &&
                     pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) {
@@ -5424,8 +5424,10 @@ static netdev_tx_t tg3_start_xmit_dma_bug(struct sk_buff *skb,
                                                                  IPPROTO_TCP,
                                                                  0);
 
-                if ((tp->tg3_flags2 & TG3_FLG2_HW_TSO) ||
-                    (GET_ASIC_REV(tp->pci_chip_rev_id) == ASIC_REV_5705)) {
+                if (tp->tg3_flags2 & TG3_FLG2_HW_TSO_2)
+                        mss |= hdr_len << 9;
+                else if ((tp->tg3_flags2 & TG3_FLG2_HW_TSO_1) ||
+                         GET_ASIC_REV(tp->pci_chip_rev_id) == ASIC_REV_5705) {
                         if (tcp_opt_len || iph->ihl > 5) {
                                 int tsflags;
 
@@ -5460,6 +5462,9 @@ static netdev_tx_t tg3_start_xmit_dma_bug(struct sk_buff *skb,
 
         would_hit_hwbug = 0;
 
+        if ((tp->tg3_flags3 & TG3_FLG3_SHORT_DMA_BUG) && len <= 8)
+                would_hit_hwbug = 1;
+
         if ((tp->tg3_flags3 & TG3_FLG3_4G_DMA_BNDRY_BUG) &&
             tg3_4g_overflow_test(mapping, len))
                 would_hit_hwbug = 1;
@@ -5489,6 +5494,10 @@ static netdev_tx_t tg3_start_xmit_dma_bug(struct sk_buff *skb,
 
                         tnapi->tx_buffers[entry].skb = NULL;
 
+                        if ((tp->tg3_flags3 & TG3_FLG3_SHORT_DMA_BUG) &&
+                            len <= 8)
+                                would_hit_hwbug = 1;
+
                         if ((tp->tg3_flags3 & TG3_FLG3_4G_DMA_BNDRY_BUG) &&
                             tg3_4g_overflow_test(mapping, len))
                                 would_hit_hwbug = 1;
@@ -12625,8 +12634,12 @@ static int __devinit tg3_get_invariants(struct tg3 *tp)
         }
 
         if (!(tp->tg3_flags3 & TG3_FLG3_5755_PLUS)) {
-                tp->tg3_flags3 |= TG3_FLG3_4G_DMA_BNDRY_BUG;
-                tp->tg3_flags3 |= TG3_FLG3_40BIT_DMA_LIMIT_BUG;
+                if (GET_ASIC_REV(tp->pci_chip_rev_id) == ASIC_REV_5906)
+                        tp->tg3_flags3 |= TG3_FLG3_SHORT_DMA_BUG;
+                else {
+                        tp->tg3_flags3 |= TG3_FLG3_4G_DMA_BNDRY_BUG;
+                        tp->tg3_flags3 |= TG3_FLG3_40BIT_DMA_LIMIT_BUG;
+                }
         }
 
         if (!(tp->tg3_flags2 & TG3_FLG2_5705_PLUS) ||
@@ -13987,8 +14000,7 @@ static int __devinit tg3_init_one(struct pci_dev *pdev,
                 goto err_out_iounmap;
         }
 
-        if ((tp->tg3_flags3 & TG3_FLG3_5755_PLUS) ||
-            GET_ASIC_REV(tp->pci_chip_rev_id) == ASIC_REV_5906)
+        if (tp->tg3_flags3 & TG3_FLG3_5755_PLUS)
                 dev->netdev_ops = &tg3_netdev_ops;
         else
                 dev->netdev_ops = &tg3_netdev_ops_dma_bug;
diff --git a/drivers/net/tg3.h b/drivers/net/tg3.h
index b603810b4e9b..a5568a149748 100644
--- a/drivers/net/tg3.h
+++ b/drivers/net/tg3.h
@@ -2761,6 +2761,7 @@ struct tg3 {
 #define TG3_FLG3_ENABLE_RSS             0x00020000
 #define TG3_FLG3_4G_DMA_BNDRY_BUG       0x00080000
 #define TG3_FLG3_40BIT_DMA_LIMIT_BUG    0x00100000
+#define TG3_FLG3_SHORT_DMA_BUG          0x00200000
 
         struct timer_list               timer;
         u16                             timer_counter;