net: cadence: macb: add ethtool EEE support

Implement ethtool get_eee and set_eee operations for the Cadence GEM
MAC, delegating to phylink for PHY-level EEE negotiation state.

The MAC-level LPI control (TXLPIEN) is not manipulated directly in the
ethtool ops. Instead, phylink_ethtool_set_eee() updates the PHY's EEE
advertisement, which triggers link renegotiation. The mac_link_up
callback then checks the negotiated EEE state and enables LPI
accordingly.

Signed-off-by: Nicolai Buchwitz <nb@tipi-net.de>

Author: nbuchwitz

drivers/net/ethernet/cadence/macb_main.c

@@ -3595,6 +3595,32 @@ static int macb_set_ringparam(struct net_device *netdev,
 	return 0;
 }
 
+static int macb_get_eee(struct net_device *ndev, struct ethtool_keee *edata)
+{
+	struct macb *bp = netdev_priv(ndev);
+
+	if (!(bp->caps & MACB_CAPS_EEE))
+		return -EOPNOTSUPP;
+
+	return phylink_ethtool_get_eee(bp->phylink, edata);
+}
+
+static int macb_set_eee(struct net_device *ndev, struct ethtool_keee *edata)
+{
+	struct macb *bp = netdev_priv(ndev);
+
+	if (!(bp->caps & MACB_CAPS_EEE))
+		return -EOPNOTSUPP;
+
+	/*
+	 * Don't directly control TXLPIEN here. phylink_ethtool_set_eee()
+	 * updates the PHY, which will bounce the link if tx_lpi_enabled
+	 * changes. That triggers mac_link_down/mac_link_up where we
+	 * enable/disable TXLPIEN based on the negotiated state.
+	 */
+	return phylink_ethtool_set_eee(bp->phylink, edata);
+}
+
 #ifdef CONFIG_MACB_USE_HWSTAMP
 static unsigned int gem_get_tsu_rate(struct macb *bp)
 {
@@ -4010,6 +4036,8 @@ static const struct ethtool_ops gem_ethtool_ops = {
 	.set_ringparam		= macb_set_ringparam,
 	.get_rxnfc			= gem_get_rxnfc,
 	.set_rxnfc			= gem_set_rxnfc,
+	.get_eee		= macb_get_eee,
+	.set_eee		= macb_set_eee,
 	.nway_reset		= phy_ethtool_nway_reset,
 };