Re: [PATCH net-next v6 0/3] net: phylink: wait for a PHY that probes after the MAC

[Paolo Abeni <pabeni@redhat.com>]

On 10/6/26 14:47, Aleksei Sviridkin wrote:
> On the Keenetic KN-1012 (MT7981B with an MT7531 switch), the Airoha
> EN8811H behind lan4 has its PHY driver built as a module on the root
> filesystem. The switch sets up its ports before that filesystem is
> mounted, so the port is validated against the generic driver, fails its
> phy-mode and stays dead for the uptime. DSA does not retry it.
> 
> Patch 1 lets the PHY node say so with needs-host-firmware. Patch 2 makes
> phylink poll for such a PHY instead of giving up, for a MAC that opts
> in. Patch 3 opts in DSA user ports of switch drivers that set a flag,
> and sets it in mt7530.
> 
> The poller can still lose a race against an unbind of the PHY driver,
> between its readiness check and the attach. That window is phylib's:
> any phy_attach_direct() caller racing an unbind has it. The attach
> guard series [1] closes it.
> 
> Tested on that board with the series backported to its OpenWrt 6.18
> kernel, together with a940003f44e7 and 07d995873960 (the mt7530
> .get_stats64 atomic-context fix). The kernel had lockdep and
> DEBUG_ATOMIC_SLEEP on. Local debug parameters, not part of the series,
> drove the error paths. They fail the connect after a successful attach,
> ignore the opt-in, fail the generic attach of a PHY with no driver, and
> add a sleep after the switch shutdown.
> 
>   - boot: the PHY driver loaded its firmware at 8.7 s. lan4 attached at
>     26.3 s, when the port was brought up. Link up at 1 Gb/s.
>   - port kept down for 10 s with the PHY driver bound: no poll and no
>     attach. "ip link set lan4 up" attached it a second later.
>   - opt-in ignored: the old behaviour, the generic driver took the PHY.
>   - two injected failures: "failed to connect late PHY: -EIO" twice, a
>     second apart, and the third attempt attached. Link up at 1 Gb/s.
>   - failures that do not stop: four attempts and one "giving up". No
>     poll after that, also not after a down/up.
>   - four failed generic attaches with no driver bound: nothing logged as
>     a failure and no retry spent. The port attached once the driver
>     bound.
>   - switch unbound while the poller waited: nothing oopsed.
>   - reboot with a 3 s sleep after the switch shutdown: the poll ran
>     every second up to the shutdown and not once in the sleep. On v5 the
>     same test polled 3 times in the sleep.
> 
> No in-tree device tree sets needs-host-firmware yet. The board is
> supported out of tree, in OpenWrt.
I'm sorry to give this feedback this late, but AI flood forces this
workflow on us.

The above looks like a significant amount of complexity for OoT driver,
and I understand it could be solved with a different kconf?

/P