[PATCH net-next v3 3/4] net: mdio: defer supplier sync during OF population

[James Hilliard <james.hilliard1@gmail.com>]

The MDIO bus class device is fully added before the OF helper creates its
PHY children. Once driverless class devices complete their managed links,
the bus proxy links are retired at the end of __mdiobus_register(), before
PHY package member links have been installed.

Pause supplier sync-state callbacks across both MDIO bus registration and
OF child population. Each member PHY acquires its real package supplier
links before the matching resume, so suppliers cannot observe the interval
between proxy retirement and member registration.

Use the existing nestable device-link deferral mechanism, export it for
modular OF MDIO code and resume it on every success and error path.

Fixes: 385ef48f4686 ("net: phy: add support for scanning PHY in PHY packages nodes")
Signed-off-by: James Hilliard <james.hilliard1@gmail.com>

---
Changes v2 -> v3:
  - Replace MDIO-specific proxy-link deletion with scoped sync-state
    deferral around bus and child population
  - Put the deferral in place before enabling generic class-device proxy
    retirement so every intermediate patch remains safe
---
 drivers/base/core.c        |  2 ++
 drivers/net/mdio/of_mdio.c | 10 +++++++---
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index cf3f4133391d..d2f9ff65138c 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -1256,6 +1256,7 @@ void device_links_supplier_sync_state_pause(void)
 	defer_sync_state_count++;
 	device_links_write_unlock();
 }
+EXPORT_SYMBOL_GPL(device_links_supplier_sync_state_pause);
 
 void device_links_supplier_sync_state_resume(void)
 {
@@ -1284,6 +1285,7 @@ void device_links_supplier_sync_state_resume(void)
 
 	device_links_flush_sync_list(&sync_list, NULL);
 }
+EXPORT_SYMBOL_GPL(device_links_supplier_sync_state_resume);
 
 static int sync_state_resume_initcall(void)
 {
diff --git a/drivers/net/mdio/of_mdio.c b/drivers/net/mdio/of_mdio.c
index ff540049b847..9b73fd8eed41 100644
--- a/drivers/net/mdio/of_mdio.c
+++ b/drivers/net/mdio/of_mdio.c
@@ -243,9 +243,10 @@ int __of_mdiobus_register(struct mii_bus *mdio, struct device_node *np,
 	of_property_read_u32(np, "reset-post-delay-us", &mdio->reset_post_delay_us);
 
 	/* Register the MDIO bus */
+	device_links_supplier_sync_state_pause();
 	rc = __mdiobus_register(mdio, owner);
 	if (rc)
-		return rc;
+		goto resume;
 
 	/* Loop over the child nodes and register a phy_device for each phy */
 	rc = __of_mdiobus_parse_phys(mdio, np, &scanphys);
@@ -253,7 +254,7 @@ int __of_mdiobus_register(struct mii_bus *mdio, struct device_node *np,
 		goto unregister;
 
 	if (!scanphys)
-		return 0;
+		goto resume;
 
 	/* auto scan for PHYs with empty reg property */
 	for_each_available_child_of_node(np, child) {
@@ -285,12 +286,15 @@ int __of_mdiobus_register(struct mii_bus *mdio, struct device_node *np,
 		}
 	}
 
-	return 0;
+	rc = 0;
+	goto resume;
 
 put_unregister:
 	of_node_put(child);
 unregister:
 	mdiobus_unregister(mdio);
+resume:
+	device_links_supplier_sync_state_resume();
 	return rc;
 }
 EXPORT_SYMBOL(__of_mdiobus_register);

-- 
2.53.0