linux-kernel - [PATCH net-next] net: dsa: bcm_sf2: Ensure that MDIO diversion is used

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Date:   Wed,  2 Sep 2020 14:03:27 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     netdev@...r.kernel.org
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH net-next] net: dsa: bcm_sf2: Ensure that MDIO diversion is used

Registering our slave MDIO bus outside of the OF infrastructure is
necessary in order to avoid creating double references of the same
Device Tree nodes, however it is not sufficient to guarantee that the
MDIO bus diversion is used because of_phy_connect() will still resolve
to a valid PHY phandle and it will connect to the PHY using its parent
MDIO bus which is still the SF2 master MDIO bus.

Ensure that of_phy_connect() does not suceed by removing any phandle
reference for the PHY we need to divert. This forces the DSA code to use
the DSA slave_mii_bus that we register and ensures the MDIO diversion is
being used.

Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
---
 drivers/net/dsa/bcm_sf2.c | 31 +++++++++++++++++++++++++++++--
 1 file changed, 29 insertions(+), 2 deletions(-)

diff --git a/drivers/net/dsa/bcm_sf2.c b/drivers/net/dsa/bcm_sf2.c
index 1c7fbb6f0447..8e215c148487 100644
--- a/drivers/net/dsa/bcm_sf2.c
+++ b/drivers/net/dsa/bcm_sf2.c
@@ -489,9 +489,11 @@ static void bcm_sf2_identify_ports(struct bcm_sf2_priv *priv,
 static int bcm_sf2_mdio_register(struct dsa_switch *ds)
 {
 	struct bcm_sf2_priv *priv = bcm_sf2_to_priv(ds);
-	struct device_node *dn;
+	struct device_node *dn, *child;
+	struct phy_device *phydev;
+	struct property *prop;
 	static int index;
-	int err;
+	int err, reg;
 
 	/* Find our integrated MDIO bus node */
 	dn = of_find_compatible_node(NULL, NULL, "brcm,unimac-mdio");
@@ -534,6 +536,31 @@ static int bcm_sf2_mdio_register(struct dsa_switch *ds)
 	priv->slave_mii_bus->parent = ds->dev->parent;
 	priv->slave_mii_bus->phy_mask = ~priv->indir_phy_mask;
 
+	/* We need to make sure that of_phy_connect() will not work by
+	 * removing the 'phandle' and 'linux,phandle' properties and
+	 * unregister the existing PHY device that was already registered.
+	 */
+	for_each_available_child_of_node(dn, child) {
+		if (of_property_read_u32(child, "reg", &reg) ||
+		    reg >= PHY_MAX_ADDR)
+			continue;
+
+		if (!(priv->indir_phy_mask & BIT(reg)))
+			continue;
+
+		prop = of_find_property(child, "phandle", NULL);
+		if (prop)
+			of_remove_property(child, prop);
+
+		prop = of_find_property(child, "linux,phandle", NULL);
+		if (prop)
+			of_remove_property(child, prop);
+
+		phydev = of_phy_find_device(child);
+		if (phydev)
+			phy_device_remove(phydev);
+	}
+
 	err = mdiobus_register(priv->slave_mii_bus);
 	if (err && dn)
 		of_node_put(dn);
-- 
2.25.1