e1000e: fix force smbus during suspend flow

Commit 861e8086 ("e1000e: move force SMBUS from enable ulp function
to avoid PHY loss issue") resolved a PHY access loss during suspend on
Meteor Lake consumer platforms, but it affected corporate systems
incorrectly.

A better fix, working for both consumer and corporate systems, was
proposed in commit bfd546a5 ("e1000e: move force SMBUS near the end
of enable_ulp function"). However, it introduced a regression on older
devices, such as [8086:15B8], [8086:15F9], [8086:15BE].

This patch aims to fix the secondary regression, by limiting the scope of
the changes to Meteor Lake platforms only.

Fixes: bfd546a5 ("e1000e: move force SMBUS near the end of enable_ulp function")
Reported-by: Todd Brandt <todd.e.brandt@intel.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218940Reported-by: Dieter Mummenschanz <dmummenschanz@web.de>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218936Signed-off-by: Vitaly Lifshits <vitaly.lifshits@intel.com>
Tested-by: Mor Bar-Gabay <morx.bar.gabay@intel.com> (A Contingent Worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20240709203123.2103296-1-anthony.l.nguyen@intel.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

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

@@ -1108,6 +1108,46 @@ static s32 e1000_platform_pm_pch_lpt(struct e1000_hw *hw, bool link)
 	return 0;
 }
 
+/**
+ *  e1000e_force_smbus - Force interfaces to transition to SMBUS mode.
+ *  @hw: pointer to the HW structure
+ *
+ *  Force the MAC and the PHY to SMBUS mode. Assumes semaphore already
+ *  acquired.
+ *
+ * Return: 0 on success, negative errno on failure.
+ **/
+static s32 e1000e_force_smbus(struct e1000_hw *hw)
+{
+	u16 smb_ctrl = 0;
+	u32 ctrl_ext;
+	s32 ret_val;
+
+	/* Switching PHY interface always returns MDI error
+	 * so disable retry mechanism to avoid wasting time
+	 */
+	e1000e_disable_phy_retry(hw);
+
+	/* Force SMBus mode in the PHY */
+	ret_val = e1000_read_phy_reg_hv_locked(hw, CV_SMB_CTRL, &smb_ctrl);
+	if (ret_val) {
+		e1000e_enable_phy_retry(hw);
+		return ret_val;
+	}
+
+	smb_ctrl |= CV_SMB_CTRL_FORCE_SMBUS;
+	e1000_write_phy_reg_hv_locked(hw, CV_SMB_CTRL, smb_ctrl);
+
+	e1000e_enable_phy_retry(hw);
+
+	/* Force SMBus mode in the MAC */
+	ctrl_ext = er32(CTRL_EXT);
+	ctrl_ext |= E1000_CTRL_EXT_FORCE_SMBUS;
+	ew32(CTRL_EXT, ctrl_ext);
+
+	return 0;
+}
+
 /**
  *  e1000_enable_ulp_lpt_lp - configure Ultra Low Power mode for LynxPoint-LP
  *  @hw: pointer to the HW structure
@@ -1165,6 +1205,14 @@ s32 e1000_enable_ulp_lpt_lp(struct e1000_hw *hw, bool to_sx)
 	if (ret_val)
 		goto out;
 
+	if (hw->mac.type != e1000_pch_mtp) {
+		ret_val = e1000e_force_smbus(hw);
+		if (ret_val) {
+			e_dbg("Failed to force SMBUS: %d\n", ret_val);
+			goto release;
+		}
+	}
+
 	/* Si workaround for ULP entry flow on i127/rev6 h/w.  Enable
 	 * LPLU and disable Gig speed when entering ULP
 	 */
@@ -1225,27 +1273,12 @@ s32 e1000_enable_ulp_lpt_lp(struct e1000_hw *hw, bool to_sx)
 	}
 
 release:
-	/* 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) {
-		e1000e_enable_phy_retry(hw);
-		hw->phy.ops.release(hw);
-		goto out;
+	if (hw->mac.type == e1000_pch_mtp) {
+		ret_val = e1000e_force_smbus(hw);
+		if (ret_val)
+			e_dbg("Failed to force SMBUS over MTL system: %d\n",
+			      ret_val);
 	}
-	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;
-	ew32(CTRL_EXT, mac_reg);
 
 	hw->phy.ops.release(hw);
 out: