net: phy: add workaround for issue where PHY driver doesn't bind to the device

[ Upstream commit c85ddecae6 ]

After switching the r8169 driver to use phylib some user reported that
their network is broken. This was caused by the genphy PHY driver being
used instead of the dedicated PHY driver for the RTL8211B. Users
reported that loading the Realtek PHY driver module upfront fixes the
issue. See also this mail thread:
https://marc.info/?t=154279781800003&r=1&w=2
The issue is quite weird and the root cause seems to be somewhere in
the base driver core. The patch works around the issue and may be
removed once the actual issue is fixed.

The Fixes tag refers to the first reported occurrence of the issue.
The issue itself may have been existing much longer and it may affect
users of other network chips as well. Users typically will recognize
this issue only if their PHY stops working when being used with the
genphy driver.

Fixes: f1e911d5d0 ("r8169: add basic phylib support")
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/net/phy/phy_device.c

@@ -1930,6 +1930,14 @@ int phy_driver_register(struct phy_driver *new_driver, struct module *owner)
 	new_driver->mdiodrv.driver.remove = phy_remove;
 	new_driver->mdiodrv.driver.owner = owner;
 
+	/* The following works around an issue where the PHY driver doesn't bind
+	 * to the device, resulting in the genphy driver being used instead of
+	 * the dedicated driver. The root cause of the issue isn't known yet
+	 * and seems to be in the base driver core. Once this is fixed we may
+	 * remove this workaround.
+	 */
+	new_driver->mdiodrv.driver.probe_type = PROBE_FORCE_SYNCHRONOUS;
+
 	retval = driver_register(&new_driver->mdiodrv.driver);
 	if (retval) {
 		pr_err("%s: Error %d in registering driver\n",