e1000e: disable K1 on PCH LOM when in PHY loopback mode

When performing the ethtool PHY loopback test on PCH-based LOMs (82577 and
82578), disable K1 (a MAC-PHY interconnect low power mode) otherwise
packets might get corrupted.
Signed-off-by: NBruce Allan <bruce.w.allan@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/e1000e/e1000.h

@@ -485,6 +485,7 @@ extern void e1000e_set_kmrn_lock_loss_workaround_ich8lan(struct e1000_hw *hw,
 extern void e1000e_igp3_phy_powerdown_workaround_ich8lan(struct e1000_hw *hw);
 extern void e1000e_gig_downshift_workaround_ich8lan(struct e1000_hw *hw);
 extern void e1000e_disable_gig_wol_ich8lan(struct e1000_hw *hw);
+extern s32 e1000_configure_k1_ich8lan(struct e1000_hw *hw, bool k1_enable);
 
 extern s32 e1000e_check_for_copper_link(struct e1000_hw *hw);
 extern s32 e1000e_check_for_fiber_link(struct e1000_hw *hw);

drivers/net/e1000e/ethtool.c

@@ -1260,6 +1260,10 @@ static int e1000_integrated_phy_loopback(struct e1000_adapter *adapter)
 
 	hw->mac.autoneg = 0;
 
+	/* Workaround: K1 must be disabled for stable 1Gbps operation */
+	if (hw->mac.type == e1000_pchlan)
+		e1000_configure_k1_ich8lan(hw, false);
+
 	if (hw->phy.type == e1000_phy_m88) {
 		/* Auto-MDI/MDIX Off */
 		e1e_wphy(hw, M88E1000_PHY_SPEC_CTRL, 0x0808);

drivers/net/e1000e/ich8lan.c

@@ -224,7 +224,6 @@ static s32 e1000_led_off_pchlan(struct e1000_hw *hw);
 static s32 e1000_set_lplu_state_pchlan(struct e1000_hw *hw, bool active);
 static void e1000_lan_init_done_ich8lan(struct e1000_hw *hw);
 static s32  e1000_k1_gig_workaround_hv(struct e1000_hw *hw, bool link);
-static s32 e1000_configure_k1_ich8lan(struct e1000_hw *hw, bool k1_enable);
 
 static inline u16 __er16flash(struct e1000_hw *hw, unsigned long reg)
 {
@@ -1023,7 +1022,7 @@ static s32 e1000_k1_gig_workaround_hv(struct e1000_hw *hw, bool link)
  *
  *  Success returns 0, Failure returns -E1000_ERR_PHY (-2)
  **/
-static s32 e1000_configure_k1_ich8lan(struct e1000_hw *hw, bool k1_enable)
+s32 e1000_configure_k1_ich8lan(struct e1000_hw *hw, bool k1_enable)
 {
 	s32 ret_val = 0;
 	u32 ctrl_reg = 0;