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Date:   Mon,  7 Feb 2022 18:15:49 +0200
From:   Vladimir Oltean <>
Cc:     Florian Fainelli <>,
        Andrew Lunn <>,
        Vivien Didelot <>,
        Vladimir Oltean <>,
        "David S. Miller" <>,
        Jakub Kicinski <>,
        Hauke Mehrtens <>,
        Sean Wang <>,
        Landen Chao <>,
        DENG Qingfang <>,
        Matthias Brugger <>,
        Claudiu Manoil <>,
        Alexandre Belloni <>,,
        Oleksij Rempel <>,
        Bartosz Golaszewski <>,
        Laurentiu Tudor <>,
        Rafael Richter <>,
        Daniel Klauer <>
Subject: [PATCH net 3/7] 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 <>
 drivers/net/dsa/bcm_sf2.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/net/dsa/bcm_sf2.c b/drivers/net/dsa/bcm_sf2.c
index 9161ce4ca352..cf82b1fa9725 100644
--- 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)
 	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) {
 		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);
+	}
 	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_free(priv->slave_mii_bus);

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