Merge branch 'dsa-devres'

Vladimir Oltean says:

====================
Fix mdiobus users with devres

Commit ac3a68d56651 ("net: phy: don't abuse devres in
devm_mdiobus_register()") by Bartosz Golaszewski has introduced two
classes of potential bugs by making the devres callback of
devm_mdiobus_alloc stop calling mdiobus_unregister.

The exact buggy circumstances are presented in the individual commit
messages. I have searched the tree for other occurrences, but at the
moment:

- for issue (a) I have no concrete proof that other buses except SPI and
  I2C suffer from it, and the only SPI or I2C device drivers that call
  of_mdiobus_alloc are the DSA drivers that leave a NULL
  ds->slave_mii_bus and a non-NULL ds->ops->phy_read, aka ksz9477,
  ksz8795, lan9303_i2c, vsc73xx-spi.

- for issue (b), all drivers which call of_mdiobus_alloc either use
  of_mdiobus_register too, or call mdiobus_unregister sometime within
  the ->remove path.

Although at this point I've seen enough strangeness caused by this
"device_del during ->shutdown" that I'm just going to copy the SPI and
I2C subsystem maintainers to this patch series, to get their feedback
whether they've had reports about things like this before. I don't think
other buses behave in this way, it forces SPI and I2C devices to have to
protect themselves from a really strange set of issues.
====================

Signed-off-by: David S. Miller <[email protected]>

2 files changed, 10 insertions, 4 deletions

diff --git a/drivers/net/dsa/realtek-smi-core.c b/drivers/net/dsa/realtek-smi-core.c
index dd2f0d6208b3..2fcfd917b876 100644
--- a/drivers/net/dsa/realtek-smi-core.c
+++ b/drivers/net/dsa/realtek-smi-core.c
@@ -368,7 +368,7 @@ int realtek_smi_setup_mdio(struct realtek_smi *smi)
 	smi->slave_mii_bus->parent = smi->dev;
 	smi->ds->slave_mii_bus = smi->slave_mii_bus;
 
-	ret = of_mdiobus_register(smi->slave_mii_bus, mdio_np);
+	ret = devm_of_mdiobus_register(smi->dev, smi->slave_mii_bus, mdio_np);
 	if (ret) {
 		dev_err(smi->dev, "unable to register MDIO bus %s\n",
 			smi->slave_mii_bus->id);
diff --git a/net/dsa/dsa2.c b/net/dsa/dsa2.c
index f54639a3a822..b29262eee00b 100644
--- a/net/dsa/dsa2.c
+++ b/net/dsa/dsa2.c
@@ -880,7 +880,7 @@ static int dsa_switch_setup(struct dsa_switch *ds)
 	devlink_params_publish(ds->devlink);
 
 	if (!ds->slave_mii_bus && ds->ops->phy_read) {
-		ds->slave_mii_bus = devm_mdiobus_alloc(ds->dev);
+		ds->slave_mii_bus = mdiobus_alloc();
 		if (!ds->slave_mii_bus) {
 			err = -ENOMEM;
 			goto teardown;
@@ -890,13 +890,16 @@ static int dsa_switch_setup(struct dsa_switch *ds)
 
 		err = mdiobus_register(ds->slave_mii_bus);
 		if (err < 0)
-			goto teardown;
+			goto free_slave_mii_bus;
 	}
 
 	ds->setup = true;
 
 	return 0;
 
+free_slave_mii_bus:
+	if (ds->slave_mii_bus && ds->ops->phy_read)
+		mdiobus_free(ds->slave_mii_bus);
 teardown:
 	if (ds->ops->teardown)
 		ds->ops->teardown(ds);
@@ -921,8 +924,11 @@ static void dsa_switch_teardown(struct dsa_switch *ds)
 	if (!ds->setup)
 		return;
 
-	if (ds->slave_mii_bus && ds->ops->phy_read)
+	if (ds->slave_mii_bus && ds->ops->phy_read) {
 		mdiobus_unregister(ds->slave_mii_bus);
+		mdiobus_free(ds->slave_mii_bus);
+		ds->slave_mii_bus = NULL;
+	}
 
 	dsa_switch_unregister_notifier(ds);