For the shared MDIO bus use case, multiple MACs will share the same MDIO bus. Therefore, these MACs all depend on this MDIO bus. If this shared MDIO bus is removed, all the PHY devices attached to this MDIO bus will also be removed. Consequently, the MAC driver should not access the PHY device, otherwise, it will lead to some potential crashes. Because the corresponding phydev and the mii_bus have been freed, some pointers have become invalid. For example. Abhishek reported a crash issue that occurred if the MDIO bus driver was removed first, followed by the MAC driver. The crash log is as below. Call trace: __list_del_entry_valid_or_report+0xa8/0xe0 __device_link_del+0x40/0xf0 device_link_put_kref+0xb4/0xc8 device_link_del+0x38/0x58 phy_detach+0x2c/0x170 phy_disconnect+0x4c/0x70 phylink_disconnect_phy+0x6c/0xc0 [phylink] stmmac_release+0x60/0x358 [stmmac] Another example is the i.MX95-15x15 platform which has two ENETC ports. When all the external PHYs are managed the EMDIO (the MDIO controller), if the enetc driver is removed after the EMDIO driver. Users will see the below crash log and the console is hanged. Call trace: _phy_state_machine+0x230/0x36c (P) phy_stop+0x74/0x190 phylink_stop+0x28/0xb8 enetc_close+0x28/0x8c __dev_close_many+0xb4/0x1d8 netif_close_many+0x8c/0x13c enetc4_pf_remove+0x2c/0x84 pci_device_remove+0x44/0xe8 To address this issue, Sarosh Hasan tried to change the devlink flag to DL_FLAG_AUTOREMOVE_SUPPLIER [1], so that the MAC driver will be removed along with the PHY driver. However, the solution does not take into account the hot-swappable PHY devices (SFP PHYs), so when the PHY device is unplugged, the MAC driver will automatically be removed, which is not the expected behavior. This issue should not exist for SFP PHYs, so based on the Sarosh's patch, the flag is changed to DL_FLAG_AUTOREMOVE_SUPPLIER for non-SFP PHYs. Reported-by: Abhishek Chauhan (ABC) Closes: https://lore.kernel.org/all/d696a426-40bb-4c1a-b42d-990fb690de5e@quicinc.com/ Link: https://lore.kernel.org/imx/20250703090041.23137-1-quic_sarohasa@quicinc.com/ # [1] Fixes: bc66fa87d4fd ("net: phy: Add link between phy dev and mac dev") Suggested-by: Maxime Chevallier Signed-off-by: Wei Fang --- v2: 1. Change the subject and update the commit message 2. Based on Maxime's suggestion, only set DL_FLAG_AUTOREMOVE_SUPPLIER flag for non-SFP PHYs. v1 link: https://lore.kernel.org/imx/20260126104409.1070403-1-wei.fang@nxp.com/ --- drivers/net/phy/phy_device.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c index 81984d4ebb7c..0494ab58ceaf 100644 --- a/drivers/net/phy/phy_device.c +++ b/drivers/net/phy/phy_device.c @@ -1771,9 +1771,17 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev, * another mac interface, so we should create a device link between * phy dev and mac dev. */ - if (dev && 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); + if (dev && bus->parent && dev->dev.parent != bus->parent) { + if (phy_on_sfp(phydev)) + phydev->devlink = device_link_add(dev->dev.parent, + &phydev->mdio.dev, + DL_FLAG_PM_RUNTIME | + DL_FLAG_STATELESS); + else + device_link_add(dev->dev.parent, &phydev->mdio.dev, + DL_FLAG_PM_RUNTIME | + DL_FLAG_AUTOREMOVE_SUPPLIER); + } return err; -- 2.34.1