igb: Use dma_wmb() instead of wmb() before doorbell writes

igb writes to doorbells to post transmit and receive descriptors;
after writing descriptors to memory but before writing to doorbells,
use dma_wmb() rather than wmb(). wmb() is more heavyweight than
necessary before doorbell writes.

On x86, this avoids SFENCEs before doorbell writes in both the
tx and rx refill paths.

Signed-off-by: Venkatesh Srinivas <venkateshs@google.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index e3a0c02..25720d9 100644 (file)
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -6031,7 +6031,7 @@ static int igb_tx_map(struct igb_ring *tx_ring,
         * We also need this memory barrier to make certain all of the
         * status bits have been updated before next_to_watch is written.
         */
-       wmb();
+       dma_wmb();
 
        /* set next_to_watch value indicating a packet is present */
        first->next_to_watch = tx_desc;
@@ -8531,7 +8531,7 @@ void igb_alloc_rx_buffers(struct igb_ring *rx_ring, u16 cleaned_count)
                 * applicable for weak-ordered memory model archs,
                 * such as IA-64).
                 */
-               wmb();
+               dma_wmb();
                writel(i, rx_ring->tail);
        }
 }