e1000e: Introduce private flag to disable K1

The K1 state reduces power consumption on ICH family network controllers
during idle periods, similarly to L1 state on PCI Express NICs. Therefore,
it is recommended and enabled by default.
However, on some systems it has been observed to have adverse side
effects, such as packet loss. It has been established through debug that
the problem may be due to firmware misconfiguration of specific systems,
interoperability with certain link partners, or marginal electrical
conditions of specific units.

These problems typically cannot be fixed in the field, and generic
workarounds to resolve the side effects on all systems, while keeping K1
enabled, were found infeasible.
Therefore, add the option for users to globally disable K1 idle state on
the adapter.

Additionally, disable K1 by default for MTL and later platforms, due to
issues reported with the current configuration.

Link: https://lore.kernel.org/intel-wired-lan/CAMqyJG3LVqfgqMcTxeaPur_Jq0oQH7GgdxRuVtRX_6TTH2mX5Q@mail.gmail.com/
Link: https://lore.kernel.org/intel-wired-lan/20250626153544.1853d106@onyx.my.domain/
Link: https://lore.kernel.org/intel-wired-lan/Z_z9EjcKtwHCQcZR@mail-itl/
Link: https://github.com/QubesOS/qubes-issues/issues/9896
Link: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2115393

Signed-off-by: Vitaly Lifshits <vitaly.lifshits@intel.com>
Reviewed-by: Timo Teräs <timo.teras@iki.fi>
Tested-by: Timo Teräs <timo.teras@iki.fi>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Reviewed-by: Dima Ruinskiy <dima.ruinskiy@intel.com>
Tested-by: Avraham Koren <Avrahamx.koren@intel.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20251016-jk-iwl-next-2025-10-15-v2-14-ff3a390d9fc6@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/intel/e1000e/e1000.h

@@ -461,6 +461,7 @@ s32 e1000e_get_base_timinca(struct e1000_adapter *adapter, u32 *timinca);
 #define FLAG2_CHECK_RX_HWTSTAMP           BIT(13)
 #define FLAG2_CHECK_SYSTIM_OVERFLOW       BIT(14)
 #define FLAG2_ENABLE_S0IX_FLOWS           BIT(15)
+#define FLAG2_DISABLE_K1		   BIT(16)
 
 #define E1000_RX_DESC_PS(R, i)	    \
 	(&(((union e1000_rx_desc_packet_split *)((R).desc))[i]))

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

@@ -26,6 +26,8 @@ struct e1000_stats {
 static const char e1000e_priv_flags_strings[][ETH_GSTRING_LEN] = {
 #define E1000E_PRIV_FLAGS_S0IX_ENABLED	BIT(0)
 	"s0ix-enabled",
+#define E1000E_PRIV_FLAGS_DISABLE_K1	BIT(1)
+	"disable-k1",
 };
 
 #define E1000E_PRIV_FLAGS_STR_LEN ARRAY_SIZE(e1000e_priv_flags_strings)
@@ -2301,26 +2303,59 @@ static u32 e1000e_get_priv_flags(struct net_device *netdev)
 	if (adapter->flags2 & FLAG2_ENABLE_S0IX_FLOWS)
 		priv_flags |= E1000E_PRIV_FLAGS_S0IX_ENABLED;
 
+	if (adapter->flags2 & FLAG2_DISABLE_K1)
+		priv_flags |= E1000E_PRIV_FLAGS_DISABLE_K1;
+
 	return priv_flags;
 }
 
 static int e1000e_set_priv_flags(struct net_device *netdev, u32 priv_flags)
 {
 	struct e1000_adapter *adapter = netdev_priv(netdev);
+	struct e1000_hw *hw = &adapter->hw;
 	unsigned int flags2 = adapter->flags2;
+	unsigned int changed;
+
+	flags2 &= ~(FLAG2_ENABLE_S0IX_FLOWS | FLAG2_DISABLE_K1);
 
-	flags2 &= ~FLAG2_ENABLE_S0IX_FLOWS;
 	if (priv_flags & E1000E_PRIV_FLAGS_S0IX_ENABLED) {
-		struct e1000_hw *hw = &adapter->hw;
-
-		if (hw->mac.type < e1000_pch_cnp)
+		if (hw->mac.type < e1000_pch_cnp) {
+			e_err("S0ix is not supported on this device\n");
 			return -EINVAL;
+		}
+
 		flags2 |= FLAG2_ENABLE_S0IX_FLOWS;
 	}
 
-	if (flags2 != adapter->flags2)
+	if (priv_flags & E1000E_PRIV_FLAGS_DISABLE_K1) {
+		if (hw->mac.type < e1000_ich8lan) {
+			e_err("Disabling K1 is not supported on this device\n");
+			return -EINVAL;
+		}
+
+		flags2 |= FLAG2_DISABLE_K1;
+	}
+
+	changed = adapter->flags2 ^ flags2;
+	if (changed)
 		adapter->flags2 = flags2;
 
+	if (changed & FLAG2_DISABLE_K1) {
+		/* reset the hardware to apply the changes */
+		while (test_and_set_bit(__E1000_RESETTING,
+					&adapter->state))
+			usleep_range(1000, 2000);
+
+		if (netif_running(adapter->netdev)) {
+			e1000e_down(adapter, true);
+			e1000e_up(adapter);
+		} else {
+			e1000e_reset(adapter);
+		}
+
+		clear_bit(__E1000_RESETTING, &adapter->state);
+	}
+
 	return 0;
 }
 

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

@@ -286,21 +286,26 @@ static void e1000_toggle_lanphypc_pch_lpt(struct e1000_hw *hw)
 }
 
 /**
- * e1000_reconfigure_k1_exit_timeout - reconfigure K1 exit timeout to
- * align to MTP and later platform requirements.
+ * e1000_reconfigure_k1_params - reconfigure Kumeran K1 parameters.
  * @hw: pointer to the HW structure
  *
+ * By default K1 is enabled after MAC reset, so this function only
+ * disables it.
+ *
  * Context: PHY semaphore must be held by caller.
  * Return: 0 on success, negative on failure
  */
-static s32 e1000_reconfigure_k1_exit_timeout(struct e1000_hw *hw)
+static s32 e1000_reconfigure_k1_params(struct e1000_hw *hw)
 {
 	u16 phy_timeout;
 	u32 fextnvm12;
 	s32 ret_val;
 
-	if (hw->mac.type < e1000_pch_mtp)
+	if (hw->mac.type < e1000_pch_mtp) {
+		if (hw->adapter->flags2 & FLAG2_DISABLE_K1)
+			return e1000_configure_k1_ich8lan(hw, false);
 		return 0;
+	}
 
 	/* Change Kumeran K1 power down state from P0s to P1 */
 	fextnvm12 = er32(FEXTNVM12);
@@ -310,6 +315,8 @@ static s32 e1000_reconfigure_k1_exit_timeout(struct e1000_hw *hw)
 
 	/* Wait for the interface the settle */
 	usleep_range(1000, 1100);
+	if (hw->adapter->flags2 & FLAG2_DISABLE_K1)
+		return e1000_configure_k1_ich8lan(hw, false);
 
 	/* Change K1 exit timeout */
 	ret_val = e1e_rphy_locked(hw, I217_PHY_TIMEOUTS_REG,
@@ -373,8 +380,8 @@ static s32 e1000_init_phy_workarounds_pchlan(struct e1000_hw *hw)
 		/* At this point the PHY might be inaccessible so don't
 		 * propagate the failure
 		 */
-		if (e1000_reconfigure_k1_exit_timeout(hw))
-			e_dbg("Failed to reconfigure K1 exit timeout\n");
+		if (e1000_reconfigure_k1_params(hw))
+			e_dbg("Failed to reconfigure K1 parameters\n");
 
 		fallthrough;
 	case e1000_pch_lpt:
@@ -473,10 +480,10 @@ static s32 e1000_init_phy_workarounds_pchlan(struct e1000_hw *hw)
 		if (hw->mac.type >= e1000_pch_mtp) {
 			ret_val = hw->phy.ops.acquire(hw);
 			if (ret_val) {
-				e_err("Failed to reconfigure K1 exit timeout\n");
+				e_err("Failed to reconfigure K1 parameters\n");
 				goto out;
 			}
-			ret_val = e1000_reconfigure_k1_exit_timeout(hw);
+			ret_val = e1000_reconfigure_k1_params(hw);
 			hw->phy.ops.release(hw);
 		}
 	}
@@ -4948,17 +4955,15 @@ static s32 e1000_init_hw_ich8lan(struct e1000_hw *hw)
 	u16 i;
 
 	e1000_initialize_hw_bits_ich8lan(hw);
-	if (hw->mac.type >= e1000_pch_mtp) {
-		ret_val = hw->phy.ops.acquire(hw);
-		if (ret_val)
-			return ret_val;
+	ret_val = hw->phy.ops.acquire(hw);
+	if (ret_val)
+		return ret_val;
 
-		ret_val = e1000_reconfigure_k1_exit_timeout(hw);
-		hw->phy.ops.release(hw);
-		if (ret_val) {
-			e_dbg("Error failed to reconfigure K1 exit timeout\n");
-			return ret_val;
-		}
+	ret_val = e1000_reconfigure_k1_params(hw);
+	hw->phy.ops.release(hw);
+	if (ret_val) {
+		e_dbg("Error failed to reconfigure K1 parameters\n");
+		return ret_val;
 	}
 
 	/* Initialize identification LED */

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

@@ -7675,6 +7675,9 @@ static int e1000_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	/* init PTP hardware clock */
 	e1000e_ptp_init(adapter);
 
+	if (hw->mac.type >= e1000_pch_mtp)
+		adapter->flags2 |= FLAG2_DISABLE_K1;
+
 	/* reset the hardware with the new settings */
 	e1000e_reset(adapter);