Re: [PATCH v2 net] net: phy: change devlink flag to AUTOREMOVE_SUPPLIER for non-SFP PHYs

Hi Wei,

On 02/02/2026 06:45, Wei Fang wrote:

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) <redacted>
Closes: https://lore.kernel.org/all/d696a426-40bb-4c1a-b42d-990fb690de5e@quicinc.com/ (local)
Link: https://lore.kernel.org/imx/20250703090041.23137-1-quic_sarohasa@quicinc.com/ (local) # [1]
Fixes: bc66fa87d4fd ("net: phy: Add link between phy dev and mac dev")
Suggested-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Signed-off-by: Wei Fang <wei.fang@nxp.com>

I gave that patch a test, with the following cases :

 - On Macchiatobin (we have PHYs that share an mdiobus).
When unbinding a PHY, the MAC dissapears as well :

#before :

# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 2048
    link/ether 00:51:82:42:42:00 brd ff:ff:ff:ff:ff:ff
3: eth1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN group default qlen 2048
    link/ether 00:51:82:42:42:01 brd ff:ff:ff:ff:ff:ff
4: eth2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 2048
    link/ether 00:51:82:42:42:02 brd ff:ff:ff:ff:ff:ff
5: eth3: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN group default qlen 2048
    link/ether 00:51:82:42:42:03 brd ff:ff:ff:ff:ff:ff

echo f212a600.mdio-mii:08 > /sys/devices/platform/cp0-bus/cp0-bus:bus@f2000000/f212a600.mdio/mdio_bus/f212a600.mdio-mii/f212a600.mdio-mii:08/driver/unbind

The MAC interface correctly disappears, but for some reason a lot of
other interfaces dissapeared as well (only eth0 is left, where I used to
have 4 different interfaces)

# after :

# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 2048
    link/ether 00:51:82:42:42:00 brd ff:ff:ff:ff:ff:ff



- I also tested the SFP PHY setup on a Cyclone V platform,
and it worked as expected (i.e. MAC didn't disappear under my
feet when removing a Copper SFP, but the devlink was still created when
the module was present) :

# ls /sys/class/devlink/ 
mdio_bus:i2c:sfp:16--platform:ff702000.ethernet

I don't have time to investigate why my interfaces are dissapearing
on mcbin, but OTHO  unbinding the devices manually isn't
something I do very often... It may or may not be related to this patch.

I'll let Russell and Andrew comment more on that as I may
still miss other cases, but as far as I can tell, this looks
OK.

Tested-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>

Maxime