[PATCH 4.14 55/64] net: mdio-mux: Handle -EPROBE_DEFER correctly

From: Sasha Levin
Date: Tue Aug 24 2021 - 13:35:00 EST

From: Saravana Kannan <saravanak@xxxxxxxxxx>

[ Upstream commit 7bd0cef5dac685f09ef8b0b2a7748ff42d284dc7 ]

When registering mdiobus children, if we get an -EPROBE_DEFER, we shouldn't
ignore it and continue registering the rest of the mdiobus children. This
would permanently prevent the deferring child mdiobus from working instead
of reattempting it in the future. So, if a child mdiobus needs to be
reattempted in the future, defer the entire mdio-mux initialization.

This fixes the issue where PHYs sitting under the mdio-mux aren't
initialized correctly if the PHY's interrupt controller is not yet ready
when the mdio-mux is being probed. Additional context in the link below.

Fixes: 0ca2997d1452 ("netdev/of/phy: Add MDIO bus multiplexer support.")
Link: https://lore.kernel.org/lkml/CAGETcx95kHrv8wA-O+-JtfH7H9biJEGJtijuPVN0V5dUKUAB3A@xxxxxxxxxxxxxx/#t
Signed-off-by: Saravana Kannan <saravanak@xxxxxxxxxx>
Reviewed-by: Andrew Lunn <andrew@xxxxxxx>
Acked-by: Marc Zyngier <maz@xxxxxxxxxx>
Tested-by: Marc Zyngier <maz@xxxxxxxxxx>
Acked-by: Kevin Hilman <khilman@xxxxxxxxxxxx>
Tested-by: Kevin Hilman <khilman@xxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
drivers/net/phy/mdio-mux.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/phy/mdio-mux.c b/drivers/net/phy/mdio-mux.c
index bb7e3f12a003..c16f875ed9ea 100644
--- a/drivers/net/phy/mdio-mux.c
+++ b/drivers/net/phy/mdio-mux.c
@@ -178,11 +178,15 @@ int mdio_mux_init(struct device *dev,
cb->mii_bus->write = mdio_mux_write;
r = of_mdiobus_register(cb->mii_bus, child_bus_node);
if (r) {
+ mdiobus_free(cb->mii_bus);
+ if (r == -EPROBE_DEFER) {
+ ret_val = r;
+ goto err_loop;
+ }
+ devm_kfree(dev, cb);
"Error: Failed to register MDIO bus for child %pOF\n",
- mdiobus_free(cb->mii_bus);
- devm_kfree(dev, cb);
} else {
cb->next = pb->children;
pb->children = cb;