e1000e: Workaround for sporadic MDI error on Meteor Lake systems

On some Meteor Lake systems accessing the PHY via the MDIO interface may
result in an MDI error. This issue happens sporadically and in most cases
a second access to the PHY via the MDIO interface results in success.

As a workaround, introduce a retry counter which is set to 3 on Meteor
Lake systems. The driver will only return an error if 3 consecutive PHY
access attempts fail. The retry mechanism is disabled in specific flows,
where MDI errors are expected.

Fixes: cc23f4f0b6b9 ("e1000e: Add support for Meteor Lake")
Suggested-by: Nikolay Mushayev <nikolay.mushayev@intel.com>
Co-developed-by: Nir Efrati <nir.efrati@intel.com>
Signed-off-by: Nir Efrati <nir.efrati@intel.com>
Signed-off-by: Vitaly Lifshits <vitaly.lifshits@intel.com>
Tested-by: Naama Meir <naamax.meir@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

1 files changed, 33 insertions, 0 deletions

diff --git a/drivers/net/ethernet/intel/e1000e/ich8lan.c b/drivers/net/ethernet/intel/e1000e/ich8lan.c
index 19e450a5bd31..d8e97669f31b 100644
--- a/drivers/net/ethernet/intel/e1000e/ich8lan.c
+++ b/drivers/net/ethernet/intel/e1000e/ich8lan.c
@@ -222,11 +222,18 @@ out:
 	if (hw->mac.type >= e1000_pch_lpt) {
 		/* Only unforce SMBus if ME is not active */
 		if (!(er32(FWSM) & E1000_ICH_FWSM_FW_VALID)) {
+			/* Switching PHY interface always returns MDI error
+			 * so disable retry mechanism to avoid wasting time
+			 */
+			e1000e_disable_phy_retry(hw);
+
 			/* Unforce SMBus mode in PHY */
 			e1e_rphy_locked(hw, CV_SMB_CTRL, &phy_reg);
 			phy_reg &= ~CV_SMB_CTRL_FORCE_SMBUS;
 			e1e_wphy_locked(hw, CV_SMB_CTRL, phy_reg);
 
+			e1000e_enable_phy_retry(hw);
+
 			/* Unforce SMBus mode in MAC */
 			mac_reg = er32(CTRL_EXT);
 			mac_reg &= ~E1000_CTRL_EXT_FORCE_SMBUS;
@@ -310,6 +317,11 @@ static s32 e1000_init_phy_workarounds_pchlan(struct e1000_hw *hw)
 		goto out;
 	}
 
+	/* There is no guarantee that the PHY is accessible at this time
+	 * so disable retry mechanism to avoid wasting time
+	 */
+	e1000e_disable_phy_retry(hw);
+
 	/* The MAC-PHY interconnect may be in SMBus mode.  If the PHY is
 	 * inaccessible and resetting the PHY is not blocked, toggle the
 	 * LANPHYPC Value bit to force the interconnect to PCIe mode.
@@ -380,6 +392,8 @@ static s32 e1000_init_phy_workarounds_pchlan(struct e1000_hw *hw)
 		break;
 	}
 
+	e1000e_enable_phy_retry(hw);
+
 	hw->phy.ops.release(hw);
 	if (!ret_val) {
 
@@ -449,6 +463,11 @@ static s32 e1000_init_phy_params_pchlan(struct e1000_hw *hw)
 
 	phy->id = e1000_phy_unknown;
 
+	if (hw->mac.type == e1000_pch_mtp) {
+		phy->retry_count = 2;
+		e1000e_enable_phy_retry(hw);
+	}
+
 	ret_val = e1000_init_phy_workarounds_pchlan(hw);
 	if (ret_val)
 		return ret_val;
@@ -1146,6 +1165,11 @@ s32 e1000_enable_ulp_lpt_lp(struct e1000_hw *hw, bool to_sx)
 	if (ret_val)
 		goto out;
 
+	/* Switching PHY interface always returns MDI error
+	 * so disable retry mechanism to avoid wasting time
+	 */
+	e1000e_disable_phy_retry(hw);
+
 	/* Force SMBus mode in PHY */
 	ret_val = e1000_read_phy_reg_hv_locked(hw, CV_SMB_CTRL, &phy_reg);
 	if (ret_val)
@@ -1153,6 +1177,8 @@ s32 e1000_enable_ulp_lpt_lp(struct e1000_hw *hw, bool to_sx)
 	phy_reg |= CV_SMB_CTRL_FORCE_SMBUS;
 	e1000_write_phy_reg_hv_locked(hw, CV_SMB_CTRL, phy_reg);
 
+	e1000e_enable_phy_retry(hw);
+
 	/* Force SMBus mode in MAC */
 	mac_reg = er32(CTRL_EXT);
 	mac_reg |= E1000_CTRL_EXT_FORCE_SMBUS;
@@ -1313,6 +1339,11 @@ static s32 e1000_disable_ulp_lpt_lp(struct e1000_hw *hw, bool force)
 		/* Toggle LANPHYPC Value bit */
 		e1000_toggle_lanphypc_pch_lpt(hw);
 
+	/* Switching PHY interface always returns MDI error
+	 * so disable retry mechanism to avoid wasting time
+	 */
+	e1000e_disable_phy_retry(hw);
+
 	/* Unforce SMBus mode in PHY */
 	ret_val = e1000_read_phy_reg_hv_locked(hw, CV_SMB_CTRL, &phy_reg);
 	if (ret_val) {
@@ -1333,6 +1364,8 @@ static s32 e1000_disable_ulp_lpt_lp(struct e1000_hw *hw, bool force)
 	phy_reg &= ~CV_SMB_CTRL_FORCE_SMBUS;
 	e1000_write_phy_reg_hv_locked(hw, CV_SMB_CTRL, phy_reg);
 
+	e1000e_enable_phy_retry(hw);
+
 	/* Unforce SMBus mode in MAC */
 	mac_reg = er32(CTRL_EXT);
 	mac_reg &= ~E1000_CTRL_EXT_FORCE_SMBUS;