Re: [PATCH net v5 2/2] Revert "net: phy: sfp: probe for RollBall I2C-to-MDIO bridge in mdio-i2c"

[Maxime Chevallier <maxime.chevallier@bootlin.com>]

Hi Petr,

On 6/27/26 19:32, Petr Wozniak wrote:
> This reverts commit 8fe125892f40 ("net: phy: sfp: probe for RollBall
> I2C-to-MDIO bridge in mdio-i2c").
> 
> That commit added a RollBall bridge probe at MDIO bus creation time, in
> i2c_mii_init_rollball(), to avoid a multi-minute PHY probe retry loop on
> modules without a bridge (e.g. RTL8261BE). The probe runs in SFP_S_INIT,
> before genuine RollBall modules have finished their firmware/bridge
> initialization, so the bridge does not yet answer CMD_READ/CMD_DONE. The
> probe times out, mdio_protocol is set to MDIO_I2C_NONE, and PHY detection
> is then skipped for genuine RollBall modules that worked before the commit.
> 
> This was confirmed on hardware by Maxime Chevallier and Aleksander
> Bajkowski: their RollBall modules no longer detect a PHY, and work again
> on v7.0 (before the bridge probing was introduced). The Sashiko static
> review flagged the same path.
> 
> Deferring the probe to PHY discovery time does not fix it either: at that
> point a slow module may still be initializing, so the probe still returns
> -ENODEV. A proper fix needs per-module init timing (a longer module_t_wait
> or a per-module quirk, per SFF-8472 the host must also wait at least 300 ms
> after insertion), which requires genuine RollBall hardware to develop and
> validate. Revert to restore the previous, working behaviour in the meantime.

Sorry this didn't work out :(

> 
> The RTL8261BE retry-loop latency that the reverted commit addressed is
> handled in our downstream tree, so reverting upstream is safe on our side.
> 
> Fixes: 8fe125892f40 ("net: phy: sfp: probe for RollBall I2C-to-MDIO bridge in mdio-i2c")
> Reported-by: Aleksander Bajkowski <olek2@wp.pl>
> Suggested-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
> Link: https://lore.kernel.org/netdev/20260624084814.20972-1-petr.wozniak@gmail.com/
> Signed-off-by: Petr Wozniak <petr.wozniak@gmail.com>

I confirm this restores rollball PHY detection on my side.

Thanks,

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

Maxime