igb: Use length to determine if descriptor is done

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.

In addition I have updated the code so that we only reset the Rx descriptor
length for descriptor zero when resetting a ring instead of having to do a
memset with 0 over the entire ring.  By doing this we can save some time on
initialization.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

1 files changed, 8 insertions, 6 deletions

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index cf7ee9cdac6f..1d76d3a90a17 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -3720,6 +3720,7 @@ void igb_configure_rx_ring(struct igb_adapter *adapter,
                            struct igb_ring *ring)
 {
         struct e1000_hw *hw = &adapter->hw;
+        union e1000_adv_rx_desc *rx_desc;
         u64 rdba = ring->dma;
         int reg_idx = ring->reg_idx;
         u32 srrctl = 0, rxdctl = 0;
@@ -3758,6 +3759,10 @@ void igb_configure_rx_ring(struct igb_adapter *adapter,
         rxdctl |= IGB_RX_HTHRESH << 8;
         rxdctl |= IGB_RX_WTHRESH << 16;
 
+        /* initialize Rx descriptor 0 */
+        rx_desc = IGB_RX_DESC(ring, 0);
+        rx_desc->wb.upper.length = 0;
+
         /* enable receive descriptor fetching */
         rxdctl |= E1000_RXDCTL_QUEUE_ENABLE;
         wr32(E1000_RXDCTL(reg_idx), rxdctl);
@@ -3973,9 +3978,6 @@ static void igb_clean_rx_ring(struct igb_ring *rx_ring)
         size = sizeof(struct igb_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;
@@ -7172,7 +7174,7 @@ static int igb_clean_rx_irq(struct igb_q_vector *q_vector, const int budget)
 
                 rx_desc = IGB_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
@@ -7312,8 +7314,8 @@ void igb_alloc_rx_buffers(struct igb_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);