e1000e: 82577: workaround for link drop issue

When connected to certain switches, the 82577 PHY might drop link
unexpectedly.  Work around the issue by setting the Mean Square Error
higher than the hardware default.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/e1000e/ich8lan.c

@@ -157,7 +157,8 @@
 #define I82579_EMI_ADDR         0x10
 #define I82579_EMI_DATA         0x11
 #define I82579_LPI_UPDATE_TIMER 0x4805	/* in 40ns units + 40 ns base value */
-#define I82579_MSE_THRESHOLD    0x084F	/* Mean Square Error Threshold */
+#define I82579_MSE_THRESHOLD    0x084F	/* 82579 Mean Square Error Threshold */
+#define I82577_MSE_THRESHOLD    0x0887	/* 82577 Mean Square Error Threshold */
 #define I82579_MSE_LINK_DOWN    0x2411	/* MSE count before dropping link */
 #define I217_EEE_ADVERTISEMENT  0x8001	/* IEEE MMD Register 7.60 */
 #define I217_EEE_LP_ABILITY     0x8002	/* IEEE MMD Register 7.61 */
@@ -1809,6 +1810,11 @@ static s32 e1000_hv_phy_workarounds_ich8lan(struct e1000_hw *hw)
 	if (ret_val)
 		goto release;
 	ret_val = e1e_wphy_locked(hw, BM_PORT_GEN_CFG, phy_data & 0x00FF);
+	if (ret_val)
+		goto release;
+
+	/* set MSE higher to enable link to stay up when noise is high */
+	ret_val = e1000_write_emi_reg_locked(hw, I82577_MSE_THRESHOLD, 0x0034);
 release:
 	hw->phy.ops.release(hw);