net: phy: fix phy_ethtool_set_eee() incorrectly enabling LPI

When phy_ethtool_set_eee_noneg() detects a change in the LPI
parameters, it attempts to update phylib state and trigger the link
to cycle so the MAC sees the updated parameters.

However, in doing so, it sets phydev->enable_tx_lpi depending on
whether the EEE configuration allows the MAC to generate LPI without
taking into account the result of negotiation.

This can be demonstrated with a 1000base-T FD interface by:

 # ethtool --set-eee eno0 advertise 8   # cause EEE to be not negotiated
 # ethtool --set-eee eno0 tx-lpi off
 # ethtool --set-eee eno0 tx-lpi on

This results in being true, despite EEE not having been negotiated and:
 # ethtool --show-eee eno0
	EEE status: enabled - inactive
	Tx LPI: 250 (us)
	Supported EEE link modes:  100baseT/Full
	                           1000baseT/Full
	Advertised EEE link modes:  100baseT/Full
	                                         1000baseT/Full

Fix this by keeping track of whether EEE was negotiated via a new
eee_active member in struct phy_device, and include this state in
the decision whether phydev->enable_tx_lpi should be set.

Fixes: 3e43b90 ("net: phy: Immediately call adjust_link if only tx_lpi_enabled changes")
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://patch.msgid.link/E1tErSe-005RhB-2R@rmk-PC.armlinux.org.uk
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Author: Russell King (Oracle)

drivers/net/phy/phy-c45.c

@@ -1530,7 +1530,7 @@ int genphy_c45_ethtool_get_eee(struct phy_device *phydev,
 		return ret;
 
 	data->eee_enabled = is_enabled;
-	data->eee_active = ret;
+	data->eee_active = phydev->eee_active;
 	linkmode_copy(data->supported, phydev->supported_eee);
 
 	return 0;

drivers/net/phy/phy.c

@@ -990,14 +990,14 @@ static int phy_check_link_status(struct phy_device *phydev)
 		phydev->state = PHY_RUNNING;
 		err = genphy_c45_eee_is_active(phydev,
 					       NULL, NULL, NULL);
-		if (err <= 0)
-			phydev->enable_tx_lpi = false;
-		else
-			phydev->enable_tx_lpi = phydev->eee_cfg.tx_lpi_enabled;
+		phydev->eee_active = err > 0;
+		phydev->enable_tx_lpi = phydev->eee_cfg.tx_lpi_enabled &&
+					phydev->eee_active;
 
 		phy_link_up(phydev);
 	} else if (!phydev->link && phydev->state != PHY_NOLINK) {
 		phydev->state = PHY_NOLINK;
+		phydev->eee_active = false;
 		phydev->enable_tx_lpi = false;
 		phy_link_down(phydev);
 	}
@@ -1685,15 +1685,21 @@ EXPORT_SYMBOL(phy_ethtool_get_eee);
 static void phy_ethtool_set_eee_noneg(struct phy_device *phydev,
 				      const struct eee_config *old_cfg)
 {
-	if (phydev->eee_cfg.tx_lpi_enabled != old_cfg->tx_lpi_enabled ||
+	bool enable_tx_lpi;
+
+	if (!phydev->link)
+		return;
+
+	enable_tx_lpi = phydev->eee_cfg.tx_lpi_enabled && phydev->eee_active;
+
+	if (phydev->enable_tx_lpi != enable_tx_lpi ||
 	    phydev->eee_cfg.tx_lpi_timer != old_cfg->tx_lpi_timer) {
-		phydev->enable_tx_lpi = eeecfg_mac_can_tx_lpi(&phydev->eee_cfg);
-		if (phydev->link) {
-			phydev->link = false;
-			phy_link_down(phydev);
-			phydev->link = true;
-			phy_link_up(phydev);
-		}
+		phydev->enable_tx_lpi = false;
+		phydev->link = false;
+		phy_link_down(phydev);
+		phydev->enable_tx_lpi = enable_tx_lpi;
+		phydev->link = true;
+		phy_link_up(phydev);
 	}
 }
 

include/linux/phy.h

@@ -602,6 +602,7 @@ struct macsec_ops;
  * @supported_eee: supported PHY EEE linkmodes
  * @advertising_eee: Currently advertised EEE linkmodes
  * @enable_tx_lpi: When True, MAC should transmit LPI to PHY
+ * @eee_active: phylib private state, indicating that EEE has been negotiated
  * @eee_cfg: User configuration of EEE
  * @lp_advertising: Current link partner advertised linkmodes
  * @host_interfaces: PHY interface modes supported by host
@@ -723,6 +724,7 @@ struct phy_device {
 	/* Energy efficient ethernet modes which should be prohibited */
 	__ETHTOOL_DECLARE_LINK_MODE_MASK(eee_broken_modes);
 	bool enable_tx_lpi;
+	bool eee_active;
 	struct eee_config eee_cfg;
 
 	/* Host supported PHY interface types. Should be ignored if empty. */