net: dsa: bcm_sf2: don't use devres for mdiobus

As explained in commits:
74b6d7d13307 ("net: dsa: realtek: register the MDIO bus under devres")
5135e96a3dd2 ("net: dsa: don't allocate the slave_mii_bus using devres")

mdiobus_free() will panic when called from devm_mdiobus_free() <-
devres_release_all() <- __device_release_driver(), and that mdiobus was
not previously unregistered.

The Starfighter 2 is a platform device, so the initial set of
constraints that I thought would cause this (I2C or SPI buses which call
->remove on ->shutdown) do not apply. But there is one more which
applies here.

If the DSA master itself is on a bus that calls ->remove from ->shutdown
(like dpaa2-eth, which is on the fsl-mc bus), there is a device link
between the switch and the DSA master, and device_links_unbind_consumers()
will unbind the bcm_sf2 switch driver on shutdown.

So the same treatment must be applied to all DSA switch drivers, which
is: either use devres for both the mdiobus allocation and registration,
or don't use devres at all.

The bcm_sf2 driver has the code structure in place for orderly mdiobus
removal, so just replace devm_mdiobus_alloc() with the non-devres
variant, and add manual free where necessary, to ensure that we don't
let devres free a still-registered bus.

Fixes: ac3a68d56651 ("net: phy: don't abuse devres in devm_mdiobus_register()")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/dsa/bcm_sf2.c b/drivers/net/dsa/bcm_sf2.c
index 33499fcd88484eb77031eebcf660b08232f8236b..6afb5db8244cd1650426a646988f3feb3b07c3d4 100644 (file)
--- a/drivers/net/dsa/bcm_sf2.c
+++ b/drivers/net/dsa/bcm_sf2.c
@@ -621,7 +621,7 @@ static int bcm_sf2_mdio_register(struct dsa_switch *ds)
        get_device(&priv->master_mii_bus->dev);
        priv->master_mii_dn = dn;
 
-       priv->slave_mii_bus = devm_mdiobus_alloc(ds->dev);
+       priv->slave_mii_bus = mdiobus_alloc();
        if (!priv->slave_mii_bus) {
                of_node_put(dn);
                return -ENOMEM;
@@ -681,8 +681,10 @@ static int bcm_sf2_mdio_register(struct dsa_switch *ds)
        }
 
        err = mdiobus_register(priv->slave_mii_bus);
-       if (err && dn)
+       if (err && dn) {
+               mdiobus_free(priv->slave_mii_bus);
                of_node_put(dn);
+       }
 
        return err;
 }
@@ -690,6 +692,7 @@ static int bcm_sf2_mdio_register(struct dsa_switch *ds)
 static void bcm_sf2_mdio_unregister(struct bcm_sf2_priv *priv)
 {
        mdiobus_unregister(priv->slave_mii_bus);
+       mdiobus_free(priv->slave_mii_bus);
        of_node_put(priv->master_mii_dn);
 }