tg3: Avoid tx lockups on 5755+ devices

In certain edge conditions, internal tx resources can get corrupted.
This patch enables a bit that will fix the problem.
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>

drivers/net/tg3.c

@@ -8214,6 +8214,9 @@ static int tg3_reset_hw(struct tg3 *tp, int reset_phy)
 	}
 
 	tp->tx_mode = TX_MODE_ENABLE;
+	if ((tp->tg3_flags3 & TG3_FLG3_5755_PLUS) ||
+	    GET_ASIC_REV(tp->pci_chip_rev_id) == ASIC_REV_5906)
+		tp->tx_mode |= TX_MODE_MBUF_LOCKUP_FIX;
 	tw32_f(MAC_TX_MODE, tp->tx_mode);
 	udelay(100);
 

drivers/net/tg3.h

@@ -469,6 +469,7 @@
 #define  TX_MODE_FLOW_CTRL_ENABLE	 0x00000010
 #define  TX_MODE_BIG_BCKOFF_ENABLE	 0x00000020
 #define  TX_MODE_LONG_PAUSE_ENABLE	 0x00000040
+#define  TX_MODE_MBUF_LOCKUP_FIX	 0x00000100
 #define MAC_TX_STATUS			0x00000460
 #define  TX_STATUS_XOFFED		 0x00000001
 #define  TX_STATUS_SENT_XOFF		 0x00000002