e1000e: workaround a Tx hang on 82577/82578

With bi-directional stress traffic, the receiver could hang causing the
hardware to stop and a "Detected Tx Unit Hang" message dumped to the system
logfile.  Temporarily workaround this issue by disabling Tx flow control by
default.  The issue is currently being investigated and a follow-on patch
will be provided to revert this when it is resolved.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 2 deletions

diff --git a/drivers/net/e1000e/ich8lan.c b/drivers/net/e1000e/ich8lan.c
index b69c8190da30..9e23f50fb9cd 100644
--- a/drivers/net/e1000e/ich8lan.c
+++ b/drivers/net/e1000e/ich8lan.c
@@ -2348,8 +2348,13 @@ static s32 e1000_setup_link_ich8lan(struct e1000_hw *hw)
          * the default flow control setting, so we explicitly
          * set it to full.
          */
-        if (hw->fc.requested_mode == e1000_fc_default)
-                hw->fc.requested_mode = e1000_fc_full;
+        if (hw->fc.requested_mode == e1000_fc_default) {
+                /* Workaround h/w hang when Tx flow control enabled */
+                if (hw->mac.type == e1000_pchlan)
+                        hw->fc.requested_mode = e1000_fc_rx_pause;
+                else
+                        hw->fc.requested_mode = e1000_fc_full;
+        }
 
         /*
          * Save off the requested flow control mode for use later.  Depending