net: dsa: warn if phylink_mac_link_state returns error

Issue a warning to the kernel log if phylink_mac_link_state() returns
an error. This should not occur, but let's make it visible.
Signed-off-by: NRussell King <rmk+kernel@armlinux.org.uk>
Reviewed-by: NAndrew Lunn <andrew@lunn.ch>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/dsa/port.c

@@ -457,6 +457,7 @@ static void dsa_port_phylink_mac_pcs_get_state(struct phylink_config *config,
 {
 	struct dsa_port *dp = container_of(config, struct dsa_port, pl_config);
 	struct dsa_switch *ds = dp->ds;
+	int err;
 
 	/* Only called for inband modes */
 	if (!ds->ops->phylink_mac_link_state) {
@@ -464,8 +465,12 @@ static void dsa_port_phylink_mac_pcs_get_state(struct phylink_config *config,
 		return;
 	}
 
-	if (ds->ops->phylink_mac_link_state(ds, dp->index, state) < 0)
+	err = ds->ops->phylink_mac_link_state(ds, dp->index, state);
+	if (err < 0) {
+		dev_err(ds->dev, "p%d: phylink_mac_link_state() failed: %d\n",
+			dp->index, err);
 		state->link = 0;
+	}
 }
 
 static void dsa_port_phylink_mac_config(struct phylink_config *config,