--- zzzz-none-000/linux-3.10.107/drivers/net/ethernet/intel/ixgbe/ixgbe_dcb_82599.c	2017-06-27 09:49:32.000000000 +0000
+++ scorpion-7490-727/linux-3.10.107/drivers/net/ethernet/intel/ixgbe/ixgbe_dcb_82599.c	2021-02-04 17:41:59.000000000 +0000
@@ -20,6 +20,7 @@
   the file called "COPYING".
 
   Contact Information:
+  Linux NICS <linux.nics@intel.com>
   e1000-devel Mailing List <e1000-devel@lists.sourceforge.net>
   Intel Corporation, 5200 N.E. Elam Young Parkway, Hillsboro, OR 97124-6497
 
@@ -241,7 +242,6 @@
 			max_tc = prio_tc[i];
 	}
 
-	fcrtl = (hw->fc.low_water << 10) | IXGBE_FCRTL_XONE;
 
 	/* Configure PFC Tx thresholds per TC */
 	for (i = 0; i <= max_tc; i++) {
@@ -256,9 +256,16 @@
 
 		if (enabled) {
 			reg = (hw->fc.high_water[i] << 10) | IXGBE_FCRTH_FCEN;
+			fcrtl = (hw->fc.low_water[i] << 10) | IXGBE_FCRTL_XONE;
 			IXGBE_WRITE_REG(hw, IXGBE_FCRTL_82599(i), fcrtl);
 		} else {
-			reg = IXGBE_READ_REG(hw, IXGBE_RXPBSIZE(i)) - 32;
+			/* In order to prevent Tx hangs when the internal Tx
+			 * switch is enabled we must set the high water mark
+			 * to the Rx packet buffer size - 24KB.  This allows
+			 * the Tx switch to function even under heavy Rx
+			 * workloads.
+			 */
+			reg = IXGBE_READ_REG(hw, IXGBE_RXPBSIZE(i)) - 24576;
 			IXGBE_WRITE_REG(hw, IXGBE_FCRTL_82599(i), 0);
 		}