net: mii_timestamper: fix static allocation by PHY driver

If phydev->mii_ts is set by the PHY driver, it will always be
overwritten in of_mdiobus_register_phy(). Fix it. Also make sure, that
the unregister() doesn't do anything if the mii_timestamper was provided by
the PHY driver.

Fixes: 1dca22b18421 ("net: mdio: of: Register discovered MII time stampers.")
Signed-off-by: Michael Walle <[e-mail]>
Acked-by: Richard Cochran <[e-mail]>
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/phy/mii_timestamper.c

···
 	struct mii_timestamping_desc *desc;
 	struct list_head *this;
 
+	/* mii_timestamper statically registered by the PHY driver won't use the
+	 * register_mii_timestamper() and thus don't have ->device set. Don't
+	 * try to unregister these.
+	 */
+	if (!mii_ts->device)
+		return;
+
 	mutex_lock(&tstamping_devices_lock);
 	list_for_each(this, &mii_timestamping_devices) {
 		desc = list_entry(this, struct mii_timestamping_desc, list);

drivers/of/of_mdio.c

···
 		of_node_put(child);
 		return rc;
 	}
-	phy->mii_ts = mii_ts;
+
+	/* phy->mii_ts may already be defined by the PHY driver. A
+	 * mii_timestamper probed via the device tree will still have
+	 * precedence.
+	 */
+	if (mii_ts)
+		phy->mii_ts = mii_ts;
 
 	dev_dbg(&mdio->dev, "registered phy %pOFn at address %i\n",
 		child, addr);