[Precise][PATCH 1/5] e1000e: 82579: workaround for link drop issue

[Rafael David Tinoco (Inaddy)]

From: Bruce Allan <bruce.w.allan at intel.com>

BugLink: http://bugs.launchpad.net/bugs/1425333

When connected to certain switches, the 82579 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 at intel.com>
(cherry picked from commit 4d24136c8ea03ecfdb6b8256571da8b520b92d8b)
Tested-by: Aaron Brown <aaron.f.brown at intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher at intel.com>
Signed-off-by: Rafael David Tinoco (Inaddy) <inaddy at ubuntu.com>
---
 drivers/net/ethernet/intel/e1000e/ich8lan.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/drivers/net/ethernet/intel/e1000e/ich8lan.c b/drivers/net/ethernet/intel/e1000e/ich8lan.c
index e2a80a2..1b69c2d 100644
--- a/drivers/net/ethernet/intel/e1000e/ich8lan.c
+++ b/drivers/net/ethernet/intel/e1000e/ich8lan.c
@@ -145,6 +145,8 @@
 #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_LINK_DOWN    0x2411	/* MSE count before dropping link */
 
 /* Strapping Option Register - RO */
 #define E1000_STRAP                     0x0000C
@@ -1669,6 +1671,26 @@ static s32 e1000_lv_phy_workarounds_ich8lan(struct e1000_hw *hw)
 	/* Set MDIO slow mode before any other MDIO access */
 	ret_val = e1000_set_mdio_slow_mode_hv(hw);
 
+	ret_val = hw->phy.ops.acquire(hw);
+	if (ret_val)
+		goto out;
+	ret_val = hw->phy.ops.write_reg_locked(hw, I82579_EMI_ADDR,
+					       I82579_MSE_THRESHOLD);
+	if (ret_val)
+		goto release;
+	/* set MSE higher to enable link to stay up when noise is high */
+	ret_val = hw->phy.ops.write_reg_locked(hw, I82579_EMI_DATA, 0x0034);
+	if (ret_val)
+		goto release;
+	ret_val = hw->phy.ops.write_reg_locked(hw, I82579_EMI_ADDR,
+					       I82579_MSE_LINK_DOWN);
+	if (ret_val)
+		goto release;
+	/* drop link after 5 times MSE threshold was reached */
+	ret_val = hw->phy.ops.write_reg_locked(hw, I82579_EMI_DATA, 0x0005);
+release:
+	hw->phy.ops.release(hw);
+
 out:
 	return ret_val;
 }
-- 
2.1.0