e1000e: Guarantee descriptor writeback flush success.

In rare circumstances, a descriptor writeback flush may not work if it
arrives on a specific clock cycle as a writeback request is going out.

Signed-off-by: Matthew Vick <matthew.vick@intel.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/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
index 6878601f20c54d29aa2a8384ac7f52547e03f30b..19ab2154802c171fcadaeceb82419681b51c90f2 100644 (file)
--- a/drivers/net/ethernet/intel/e1000e/netdev.c
+++ b/drivers/net/ethernet/intel/e1000e/netdev.c
@@ -1059,6 +1059,13 @@ static void e1000_print_hw_hang(struct work_struct *work)
                ew32(TIDV, adapter->tx_int_delay | E1000_TIDV_FPD);
                /* execute the writes immediately */
                e1e_flush();
+               /*
+                * Due to rare timing issues, write to TIDV again to ensure
+                * the write is successful
+                */
+               ew32(TIDV, adapter->tx_int_delay | E1000_TIDV_FPD);
+               /* execute the writes immediately */
+               e1e_flush();
                adapter->tx_hang_recheck = true;
                return;
        }
@@ -3616,6 +3623,16 @@ static void e1000e_flush_descriptors(struct e1000_adapter *adapter)
 
        /* execute the writes immediately */
        e1e_flush();
+
+       /*
+        * due to rare timing issues, write to TIDV/RDTR again to ensure the
+        * write is successful
+        */
+       ew32(TIDV, adapter->tx_int_delay | E1000_TIDV_FPD);
+       ew32(RDTR, adapter->rx_int_delay | E1000_RDTR_FPD);
+
+       /* execute the writes immediately */
+       e1e_flush();
 }
 
 static void e1000e_update_stats(struct e1000_adapter *adapter);