ixgbe: Fix FCRTH value in VM-to-VM loopback mode

The 82599 and X540 datasheets require that FCRTH be "set" for Tx
switching (VM-to-VM loopback) but it did not previously specify what
the value should be set to. It has now been determined that
the correct value is RXPBSIZE - (24*1024).

This setting is also required for later devices.

Signed-off-by: Mark Rustad <mark.d.rustad@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
index 98e1ddd..ce61b36 100644 (file)
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
@@ -2164,10 +2164,11 @@ s32 ixgbe_fc_enable_generic(struct ixgbe_hw *hw)
                        /*
                         * In order to prevent Tx hangs when the internal Tx
                         * switch is enabled we must set the high water mark
-                        * to the maximum FCRTH value.  This allows the Tx
-                        * switch to function even under heavy Rx workloads.
+                        * to the Rx packet buffer size - 24KB.  This allows
+                        * the Tx switch to function even under heavy Rx
+                        * workloads.
                         */
-                       fcrth = IXGBE_READ_REG(hw, IXGBE_RXPBSIZE(i)) - 32;
+                       fcrth = IXGBE_READ_REG(hw, IXGBE_RXPBSIZE(i)) - 24576;
                }
 
                IXGBE_WRITE_REG(hw, IXGBE_FCRTH_82599(i), fcrth);

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_dcb_82599.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_dcb_82599.c
index 3b932fe..23277ab 100644 (file)
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_dcb_82599.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_dcb_82599.c
@@ -259,7 +259,13 @@ s32 ixgbe_dcb_config_pfc_82599(struct ixgbe_hw *hw, u8 pfc_en, u8 *prio_tc)
                        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);
                }