[net-next 09/14] ixgbe: Use length to determine if descriptor is done

[Jeff Kirsher]

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

This change makes it so that we use the length of the packet instead of the
DD status bit to determine if a new descriptor is ready to be processed.
The obvious advantage is that it cuts down on reads as we don't really even
need the DD bit if going from a 0 to a non-zero value on size is enough to
inform us that the packet has been completed.

Signed-off-by: Alexander Duyck <alexander.h.du...@intel.com>
Tested-by: Andrew Bowers <andrewx.bow...@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirs...@intel.com>
---
 drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c |  2 +-
 drivers/net/ethernet/intel/ixgbe/ixgbe_main.c    | 14 ++++++++------
 2 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c 
b/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c
index 04f15092ae31..51a1695a75ee 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c
@@ -1868,7 +1868,7 @@ static u16 ixgbe_clean_test_rings(struct ixgbe_ring 
*rx_ring,
        tx_ntc = tx_ring->next_to_clean;
        rx_desc = IXGBE_RX_DESC(rx_ring, rx_ntc);
 
-       while (ixgbe_test_staterr(rx_desc, IXGBE_RXD_STAT_DD)) {
+       while (rx_desc->wb.upper.length) {
                /* check Rx buffer */
                rx_buffer = &rx_ring->rx_buffer_info[rx_ntc];
 
diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c 
b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index 415e5ad1485a..6fc26cdacba2 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -1640,8 +1640,8 @@ void ixgbe_alloc_rx_buffers(struct ixgbe_ring *rx_ring, 
u16 cleaned_count)
                        i -= rx_ring->count;
                }
 
-               /* clear the status bits for the next_to_use descriptor */
-               rx_desc->wb.upper.status_error = 0;
+               /* clear the length for the next_to_use descriptor */
+               rx_desc->wb.upper.length = 0;
 
                cleaned_count--;
        } while (cleaned_count);
@@ -2154,7 +2154,7 @@ static int ixgbe_clean_rx_irq(struct ixgbe_q_vector 
*q_vector,
 
                rx_desc = IXGBE_RX_DESC(rx_ring, rx_ring->next_to_clean);
 
-               if (!rx_desc->wb.upper.status_error)
+               if (!rx_desc->wb.upper.length)
                        break;
 
                /* This memory barrier is needed to keep us from reading
@@ -3698,6 +3698,7 @@ void ixgbe_configure_rx_ring(struct ixgbe_adapter 
*adapter,
                             struct ixgbe_ring *ring)
 {
        struct ixgbe_hw *hw = &adapter->hw;
+       union ixgbe_adv_rx_desc *rx_desc;
        u64 rdba = ring->dma;
        u32 rxdctl;
        u8 reg_idx = ring->reg_idx;
@@ -3732,6 +3733,10 @@ void ixgbe_configure_rx_ring(struct ixgbe_adapter 
*adapter,
                rxdctl |=  0x080420;
        }
 
+       /* initialize Rx descriptor 0 */
+       rx_desc = IXGBE_RX_DESC(ring, 0);
+       rx_desc->wb.upper.length = 0;
+
        /* enable receive descriptor ring */
        rxdctl |= IXGBE_RXDCTL_ENABLE;
        IXGBE_WRITE_REG(hw, IXGBE_RXDCTL(reg_idx), rxdctl);
@@ -4940,9 +4945,6 @@ static void ixgbe_clean_rx_ring(struct ixgbe_ring 
*rx_ring)
        size = sizeof(struct ixgbe_rx_buffer) * rx_ring->count;
        memset(rx_ring->rx_buffer_info, 0, size);
 
-       /* Zero out the descriptor ring */
-       memset(rx_ring->desc, 0, rx_ring->size);
-
        rx_ring->next_to_alloc = 0;
        rx_ring->next_to_clean = 0;
        rx_ring->next_to_use = 0;
-- 
2.11.0