net: phy: Add link between phy dev and mac dev

If the external phy used by current mac interface is
managed by another mac interface, it means that this
network port cannot work independently, especially
when the system suspends and resumes, the following
trace may appear, so we should create a device link
between phy dev and mac dev.

WARNING: CPU: 0 PID: 24 at drivers/net/phy/phy.c:983 phy_error+0x20/0x68
Modules linked in:
CPU: 0 PID: 24 Comm: kworker/0:2 Not tainted 6.1.0-rc3-00011-g5aaef24b5c6d-dirty #34
Hardware name: Freescale i.MX6 SoloX (Device Tree)
Workqueue: events_power_efficient phy_state_machine
unwind_backtrace from show_stack+0x10/0x14
show_stack from dump_stack_lvl+0x68/0x90
dump_stack_lvl from __warn+0xb4/0x24c
__warn from warn_slowpath_fmt+0x5c/0xd8
warn_slowpath_fmt from phy_error+0x20/0x68
phy_error from phy_state_machine+0x22c/0x23c
phy_state_machine from process_one_work+0x288/0x744
process_one_work from worker_thread+0x3c/0x500
worker_thread from kthread+0xf0/0x114
kthread from ret_from_fork+0x14/0x28
Exception stack(0xf0951fb0 to 0xf0951ff8)

Signed-off-by: Xiaolei Wang <[e-mail]>
Tested-by: Florian Fainelli <[e-mail]>
Reviewed-by: Florian Fainelli <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/phy/phy_device.c

···
 	phy_resume(phydev);
 	phy_led_triggers_register(phydev);
 
+	/**
+	 * If the external phy used by current mac interface is managed by
+	 * another mac interface, so we should create a device link between
+	 * phy dev and mac dev.
+	 */
+	if (phydev->mdio.bus->parent && dev->dev.parent != phydev->mdio.bus->parent)
+		phydev->devlink = device_link_add(dev->dev.parent, &phydev->mdio.dev,
+						  DL_FLAG_PM_RUNTIME | DL_FLAG_STATELESS);
+
 	return err;
 
 error:
···
 	struct net_device *dev = phydev->attached_dev;
 	struct module *ndev_owner = NULL;
 	struct mii_bus *bus;
+
+	if (phydev->devlink)
+		device_link_del(phydev->devlink);
 
 	if (phydev->sysfs_links) {
 		if (dev)

include/linux/phy.h

···
  *
  * @mdio: MDIO bus this PHY is on
  * @drv: Pointer to the driver for this PHY instance
+ * @devlink: Create a link between phy dev and mac dev, if the external phy
+ *           used by current mac interface is managed by another mac interface.
  * @phy_id: UID for this device found during discovery
  * @c45_ids: 802.3-c45 Device Identifiers if is_c45.
  * @is_c45:  Set to true if this PHY uses clause 45 addressing.
···
 	/* Information about the PHY type */
 	/* And management functions */
 	struct phy_driver *drv;
+
+	struct device_link *devlink;
 
 	u32 phy_id;