[PATCH iwl-next v2 4/4] ixgbe: add IXGBE_ITR_ADAPTIVE_MASK_USECS constant

[Aleksandr Loktionov <aleksandr.loktionov@intel.com>]

From: Alexander Duyck <alexander.h.duyck@intel.com>

ixgbe_set_itr() clears the mode flag (IXGBE_ITR_ADAPTIVE_LATENCY, bit 7)
with the open-coded complement expression ~IXGBE_ITR_ADAPTIVE_LATENCY.
This is equivalent to keeping only bits [6:0], i.e. the usecs sub-field.

Add IXGBE_ITR_ADAPTIVE_MASK_USECS = IXGBE_ITR_ADAPTIVE_LATENCY - 1 =
0x7F to name this mask explicitly and replace the open-coded AND-NOT
operation with the cleaner AND form.  The two expressions are
arithmetically identical; the change improves readability.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
---
 drivers/net/ethernet/intel/ixgbe/ixgbe.h      | 1 +
 drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe.h b/drivers/net/ethernet/intel/ixgbe/ixgbe.h
index 1a7fd90..594ccb2 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe.h
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe.h
@@ -478,6 +478,7 @@ static inline unsigned int ixgbe_rx_pg_order(struct ixgbe_ring *ring)
 #define IXGBE_ITR_ADAPTIVE_MAX_USECS	84
 #define IXGBE_ITR_ADAPTIVE_LATENCY	0x80
 #define IXGBE_ITR_ADAPTIVE_BULK		0x00
+#define IXGBE_ITR_ADAPTIVE_MASK_USECS	(IXGBE_ITR_ADAPTIVE_LATENCY - 1)
 
 struct ixgbe_ring_container {
 	struct ixgbe_ring *ring;	/* pointer to linked list of rings */
diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index 7fb2ab4..8d3627c 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -2962,7 +2962,7 @@ static void ixgbe_set_itr(struct ixgbe_q_vector *q_vector)
 	new_itr = min(q_vector->rx.itr, q_vector->tx.itr);
 
 	/* Clear latency flag if set, shift into correct position */
-	new_itr &= ~IXGBE_ITR_ADAPTIVE_LATENCY;
+	new_itr &= IXGBE_ITR_ADAPTIVE_MASK_USECS;
 	new_itr <<= 2;
 
 	if (new_itr != q_vector->itr) {
-- 
2.52.0