fm10k/igb/ixgbe: Use dma_rmb on Rx descriptor reads
This change makes it so that dma_rmb is used when reading the Rx
descriptor. The advantage of dma_rmb is that it allows for a much
lower cost barrier on x86, powerpc, arm, and arm64 architectures than a
traditional memory barrier when dealing with reads that only have to
synchronize to coherent memory.
In addition I have updated the code so that it just checks to see if any
bits have been set instead of just the DD bit since the DD bit will always
be set as a part of a descriptor write-back so we just need to check for a
non-zero value being present at that memory location rather than just
checking for any specific bit. This allows the code itself to appear much
cleaner and allows the compiler more room to optimize.
Cc: Matthew Vick <matthew.vick@intel.com>
Cc: Don Skidmore <donald.c.skidmore@intel.com>
Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index 2e526d4..ff59897 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -6910,14 +6910,14 @@
rx_desc = IGB_RX_DESC(rx_ring, rx_ring->next_to_clean);
- if (!igb_test_staterr(rx_desc, E1000_RXD_STAT_DD))
+ if (!rx_desc->wb.upper.status_error)
break;
/* This memory barrier is needed to keep us from reading
* any other fields out of the rx_desc until we know the
- * RXD_STAT_DD bit is set
+ * descriptor has been written back
*/
- rmb();
+ dma_rmb();
/* retrieve a buffer from the ring */
skb = igb_fetch_rx_buffer(rx_ring, rx_desc, skb);