[PATCH 5.10 070/116] net: dsa: ar9331: register the mdiobus under devres

Greg Kroah-Hartman
2022-02-14T09:56:54Z

From: Vladimir Oltean <vladimir.oltean@nxp.com>

[ Upstream commit 50facd86e9fbc4b93fe02e5fe05776047f45dbfb ]

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 ar9331 is an MDIO 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 ar9331 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 ar9331 driver doesn't have a complex code structure for mdiobus
removal, so just replace of_mdiobus_register with the devres variant in
order to be all-devres and ensure that we don't 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>
Tested-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/dsa/qca/ar9331.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/net/dsa/qca/ar9331.c b/drivers/net/dsa/qca/ar9331.c
index 661745932a539..c33bdcf7efc58 100644
--- a/drivers/net/dsa/qca/ar9331.c
+++ b/drivers/net/dsa/qca/ar9331.c
@@ -289,7 +289,7 @@ static int ar9331_sw_mbus_init(struct ar9331_sw_priv *priv)
if (!mnp)
return -ENODEV;

- ret = of_mdiobus_register(mbus, mnp);
+ ret = devm_of_mdiobus_register(dev, mbus, mnp);
of_node_put(mnp);
if (ret)
return ret;
@@ -856,7 +856,6 @@ static void ar9331_sw_remove(struct mdio_device *mdiodev)
struct ar9331_sw_priv *priv = dev_get_drvdata(&mdiodev->dev);

irq_domain_remove(priv->irqdomain);
- mdiobus_unregister(priv->mbus);
dsa_unregister_switch(&priv->ds);

reset_control_assert(priv->sw_reset);
--
2.34.1