Re: [PATCH net v13 3/4] net: phy: take the interrupt back from the bus on detach

[Andrew Lunn]

On Thu, Oct 01, 2026 at 04:02:35PM +0300, Aleksei Sviridkin wrote:
> When a PHY's driver is a module that is not loaded yet when the MAC
> connects, the PHY gets the generic driver first. phy_probe() then
> replaces phydev->irq with PHY_POLL, because genphy has no interrupt
> support. Nothing puts the number back, so after the real driver binds
> the PHY is polled for the rest of the uptime.
> 
> Seen on a Keenetic KN-1012: the Airoha EN8811H behind an MT7531 port
> has its driver on the root filesystem. Its devicetree interrupt maps to
> irq 15, and after the real driver binds phydev->irq reads -1.
> 
> Restore the number when the PHY detaches. It comes from the bus table,
> mdiobus->irq[], where the bus or the MAC driver recorded it. Do it only
> when phy_attach_direct() bound the generic driver, since that is the
> substitution being undone; otherwise the field belongs to whoever wrote
> it. Do it before device_release_driver(), because after the release a
> probing driver can write the same field.
> 
> The store is ordered before the release rather than locked against it:
> device_release_driver() takes the device lock itself. A MAC that sets
> phydev->irq before phy_start(), as phy.rst describes, is not affected,
> since the restore runs on detach, between connections.
> 
> Tested on the KN-1012 with a 6.18 distribution kernel: phydev->irq
> reads 15 after the real driver binds, and -1 without this patch.
> 
> Fixes: 00db8189d984 ("This patch adds a PHY Abstraction Layer to the Linux Kernel, enabling ethernet drivers to remain as ignorant as is reasonable of the connected PHY's design and operation details.")
> Assisted-by: LLM
> Signed-off-by: Aleksei Sviridkin <f@xxxxxx>

Reviewed-by: Andrew Lunn <andrew@xxxxxxx>

    Andrew