bnx2x: Fix chip hanging due to TX pipe stall.

Fix a problem in which the 578xx chip hangs after running traffic, and then pulling the network cable.
This occurs since TX pipe is stalled due to missing XON indication towards the NIG.
Signed-off-by: Yaniv Rosner <yanivr@broadcom.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bnx2x/bnx2x_link.c

@@ -1667,10 +1667,20 @@ static void bnx2x_xmac_disable(struct link_params *params)
 {
 	u8 port = params->port;
 	struct bnx2x *bp = params->bp;
-	u32 xmac_base = (port) ? GRCBASE_XMAC1 : GRCBASE_XMAC0;
+	u32 pfc_ctrl, xmac_base = (port) ? GRCBASE_XMAC1 : GRCBASE_XMAC0;
 
 	if (REG_RD(bp, MISC_REG_RESET_REG_2) &
 	    MISC_REGISTERS_RESET_REG_2_XMAC) {
+		/*
+		 * Send an indication to change the state in the NIG back to XON
+		 * Clearing this bit enables the next set of this bit to get
+		 * rising edge
+		 */
+		pfc_ctrl = REG_RD(bp, xmac_base + XMAC_REG_PFC_CTRL_HI);
+		REG_WR(bp, xmac_base + XMAC_REG_PFC_CTRL_HI,
+		       (pfc_ctrl & ~(1<<1)));
+		REG_WR(bp, xmac_base + XMAC_REG_PFC_CTRL_HI,
+		       (pfc_ctrl | (1<<1)));
 		DP(NETIF_MSG_LINK, "Disable XMAC on port %x\n", port);
 		REG_WR(bp, xmac_base + XMAC_REG_CTRL, 0);
 		usleep_range(1000, 1000);