net: phylink: fix regression when binding a PHY

Some PHYs don't support clause 45 access, and return -EOPNOTSUPP from
phy_modify_mmd(), which causes phylink_bringup_phy() to fail. Prevent
this failure by allowing -EOPNOTSUPP to also mean success.

Reported-by: Jiawen Wu <[email protected]>
Tested-by: Jiawen Wu <[email protected]>
Signed-off-by: Russell King (Oracle) <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: Russell King (Oracle)

drivers/net/phy/phylink.c

@@ -2268,7 +2268,11 @@ static int phylink_bringup_phy(struct phylink *pl, struct phy_device *phy,
 	/* Explicitly configure whether the PHY is allowed to stop it's
 	 * receive clock.
 	 */
-	return phy_eee_rx_clock_stop(phy, pl->config->eee_rx_clk_stop_enable);
+	ret = phy_eee_rx_clock_stop(phy, pl->config->eee_rx_clk_stop_enable);
+	if (ret == -EOPNOTSUPP)
+		ret = 0;
+
+	return ret;
 }
 
 static int phylink_attach_phy(struct phylink *pl, struct phy_device *phy,