net: mdiobus: Set FWNODE_FLAG_NEEDS_CHILD_BOUND_ON_ADD for mdiobus parents

There are many instances of PHYs that depend on a switch to supply a
resource (Eg: interrupts). Switches also expects the PHYs to be probed
by their specific drivers as soon as they are added. If that doesn't
happen, then the switch would force the use of generic PHY drivers for
the PHY even if the PHY might have specific driver available.

fw_devlink=on by design can cause delayed probes of PHY. To avoid, this
we need to set the FWNODE_FLAG_NEEDS_CHILD_BOUND_ON_ADD for the switch's
fwnode before the PHYs are added. The most generic way to do this is to
set this flag for the parent of MDIO busses which is typically the
switch.

For more context:
https://lore.kernel.org/lkml/YTll0i6Rz3WAAYzs@lunn.ch/#t

Fixes: 53c7a47ae002 ("Revert "Revert "driver core: Set fw_devlink=on by default""")
Suggested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20210915170940.617415-4-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index 53f034fc2ef7983527faa32fc7589e93eb8f04bc..ee8313a4ac71307c0135ed63808dfa4ef5044b01 100644 (file)
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -525,6 +525,10 @@ int __mdiobus_register(struct mii_bus *bus, struct module *owner)
            NULL == bus->read || NULL == bus->write)
                return -EINVAL;
 
+       if (bus->parent && bus->parent->of_node)
+               bus->parent->of_node->fwnode.flags |=
+                                       FWNODE_FLAG_NEEDS_CHILD_BOUND_ON_ADD;
+
        BUG_ON(bus->state != MDIOBUS_ALLOCATED &&
               bus->state != MDIOBUS_UNREGISTERED);