From: Nicholas Nunley <nicholas.d.nunley@intel.com>
Date: Tue, 5 Nov 2019 04:22:14 -0800
Subject: iavf: initialize ITRN registers with correct values
Patch-mainline: v5.4-rc7
Git-commit: 4eda4e0096842764d725bcfd77471a419832b074
References: jsc#SLE-7940 bnc#1151927 5.3.15

Since commit 92418fb14750 ("i40e/i40evf: Use usec value instead of reg
value for ITR defines") the driver tracks the interrupt throttling
intervals in single usec units, although the actual ITRN registers are
programmed in 2 usec units. Most register programming flows in the driver
correctly handle the conversion, although it is currently not applied when
the registers are initialized to their default values. Most of the time
this doesn't present a problem since the default values are usually
immediately overwritten through the standard adaptive throttling mechanism,
or updated manually by the user, but if adaptive throttling is disabled and
the interval values are left alone then the incorrect value will persist.

Since the intended default interval of 50 usecs (vs. 100 usecs as
programmed) performs better for most traffic workloads, this can lead to
performance regressions.

This patch adds the correct conversion when writing the initial values to
the ITRN registers.

Signed-off-by: Nicholas Nunley <nicholas.d.nunley@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/ethernet/intel/iavf/iavf_main.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/net/ethernet/intel/iavf/iavf_main.c
+++ b/drivers/net/ethernet/intel/iavf/iavf_main.c
@@ -314,7 +314,7 @@ iavf_map_vector_to_rxq(struct iavf_adapt
 	q_vector->rx.target_itr = ITR_TO_REG(rx_ring->itr_setting);
 	q_vector->ring_mask |= BIT(r_idx);
 	wr32(hw, IAVF_VFINT_ITRN1(IAVF_RX_ITR, q_vector->reg_idx),
-	     q_vector->rx.current_itr);
+	     q_vector->rx.current_itr >> 1);
 	q_vector->rx.current_itr = q_vector->rx.target_itr;
 }
 
@@ -340,7 +340,7 @@ iavf_map_vector_to_txq(struct iavf_adapt
 	q_vector->tx.target_itr = ITR_TO_REG(tx_ring->itr_setting);
 	q_vector->num_ringpairs++;
 	wr32(hw, IAVF_VFINT_ITRN1(IAVF_TX_ITR, q_vector->reg_idx),
-	     q_vector->tx.target_itr);
+	     q_vector->tx.target_itr >> 1);
 	q_vector->tx.current_itr = q_vector->tx.target_itr;
 }