stmmac: fix and review the ptp registration.

The commit commit 7086605a6a ("stmmac: fix error check when init ptp")
breaks the procedure added by the
commit efee95f42b ("ptp_clock: future-proofing drivers against PTP
subsystem becoming optional")

So this patch tries to re-import the logic added by the latest
commit above: it makes sense to have the stmmac_ptp_register
as void function and, inside the main, the stmmac_init_ptp can fails
in case of the capability cannot be supported by the HW.

Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Cc: Alexandre TORGUE <alexandre.torgue@st.com>
Cc: Rayagond Kokatanur <rayagond@vayavyalabs.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Nicolas Pitre <nico@linaro.org>
Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/stmmac.h

@@ -145,7 +145,7 @@ int stmmac_mdio_register(struct net_device *ndev);
 int stmmac_mdio_reset(struct mii_bus *mii);
 void stmmac_set_ethtool_ops(struct net_device *netdev);
 
-int stmmac_ptp_register(struct stmmac_priv *priv);
+void stmmac_ptp_register(struct stmmac_priv *priv);
 void stmmac_ptp_unregister(struct stmmac_priv *priv);
 int stmmac_resume(struct device *dev);
 int stmmac_suspend(struct device *dev);

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -676,7 +676,9 @@ static int stmmac_init_ptp(struct stmmac_priv *priv)
 	priv->hwts_tx_en = 0;
 	priv->hwts_rx_en = 0;
 
-	return stmmac_ptp_register(priv);
+	stmmac_ptp_register(priv);
+
+	return 0;
 }
 
 static void stmmac_release_ptp(struct stmmac_priv *priv)
@@ -1710,7 +1712,7 @@ static int stmmac_hw_setup(struct net_device *dev, bool init_ptp)
 	if (init_ptp) {
 		ret = stmmac_init_ptp(priv);
 		if (ret)
-			netdev_warn(priv->dev, "PTP support cannot init.\n");
+			netdev_warn(priv->dev, "fail to init PTP.\n");
 	}
 
 #ifdef CONFIG_DEBUG_FS

drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c

@@ -177,7 +177,7 @@ static struct ptp_clock_info stmmac_ptp_clock_ops = {
  * Description: this function will register the ptp clock driver
  * to kernel. It also does some house keeping work.
  */
-int stmmac_ptp_register(struct stmmac_priv *priv)
+void stmmac_ptp_register(struct stmmac_priv *priv)
 {
 	spin_lock_init(&priv->ptp_lock);
 	priv->ptp_clock_ops = stmmac_ptp_clock_ops;
@@ -185,17 +185,10 @@ int stmmac_ptp_register(struct stmmac_priv *priv)
 	priv->ptp_clock = ptp_clock_register(&priv->ptp_clock_ops,
 					     priv->device);
 	if (IS_ERR(priv->ptp_clock)) {
-		int ret = PTR_ERR(priv->ptp_clock);
-
+		netdev_err(priv->dev, "ptp_clock_register failed\n");
 		priv->ptp_clock = NULL;
-		return ret;
-	}
-
-	spin_lock_init(&priv->ptp_lock);
-
-	netdev_dbg(priv->dev, "Added PTP HW clock successfully\n");
-
-	return 0;
+	} else if (priv->ptp_clock)
+		netdev_info(priv->dev, "registered PTP clock\n");
 }
 
 /**