ixgbe: Wait for master disable to be set

According to the datasheets, the driver should wait for the master
disable bit to read as being set before checking the status
register for master disable.
Reported-by: NDan Streetman <dan.streetman@canonical.com>
Signed-off-by: NMark Rustad <mark.d.rustad@intel.com>
Tested-by: NDarin Miller <darin.j.miller@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/ixgbe/ixgbe_common.c

 /*******************************************************************************
 
   Intel 10 Gigabit PCI Express Linux driver
-  Copyright(c) 1999 - 2014 Intel Corporation.
+  Copyright(c) 1999 - 2015 Intel Corporation.
 
   This program is free software; you can redistribute it and/or modify it
   under the terms and conditions of the GNU General Public License,
@@ -2454,6 +2454,17 @@ static s32 ixgbe_disable_pcie_master(struct ixgbe_hw *hw)
 	/* Always set this bit to ensure any future transactions are blocked */
 	IXGBE_WRITE_REG(hw, IXGBE_CTRL, IXGBE_CTRL_GIO_DIS);
 
+	/* Poll for bit to read as set */
+	for (i = 0; i < IXGBE_PCI_MASTER_DISABLE_TIMEOUT; i++) {
+		if (IXGBE_READ_REG(hw, IXGBE_CTRL) & IXGBE_CTRL_GIO_DIS)
+			break;
+		usleep_range(100, 120);
+	}
+	if (i >= IXGBE_PCI_MASTER_DISABLE_TIMEOUT) {
+		hw_dbg(hw, "GIO disable did not set - requesting resets\n");
+		goto gio_disable_fail;
+	}
+
 	/* Exit if master requests are blocked */
 	if (!(IXGBE_READ_REG(hw, IXGBE_STATUS) & IXGBE_STATUS_GIO) ||
 	    ixgbe_removed(hw->hw_addr))
@@ -2475,6 +2486,7 @@ static s32 ixgbe_disable_pcie_master(struct ixgbe_hw *hw)
 	 * again to clear out any effects they may have had on our device.
 	 */
 	hw_dbg(hw, "GIO Master Disable bit didn't clear - requesting resets\n");
+gio_disable_fail:
 	hw->mac.flags |= IXGBE_FLAGS_DOUBLE_RESET_REQUIRED;
 
 	if (hw->mac.type >= ixgbe_mac_X550)