Re: [PATCH v2 net-next] net: phy: mdio-i2c: defer RollBall bridge probe to PHY discovery

From: Jakub Kicinski <kuba@kernel.org>
To: Petr Wozniak <petr.wozniak@gmail.com>
Cc: netdev@vger.kernel.org, andrew@lunn.ch, hkallweit1@gmail.com,
	linux@armlinux.org.uk, davem@davemloft.net, edumazet@google.com,
	pabeni@redhat.com, linux-phy@lists.infradead.org,
	linux-kernel@vger.kernel.org, maxime.chevallier@bootlin.com,
	bjorn@mork.no, olek2@wp.pl
Subject: Re: [PATCH v2 net-next] net: phy: mdio-i2c: defer RollBall bridge probe to PHY discovery
Date: Mon, 8 Jun 2026 19:28:34 -0700	[thread overview]
Message-ID: <20260608192834.4244bcc9@kernel.org> (raw)
In-Reply-To: <20260605053056.1977-1-petr.wozniak@gmail.com>

On Fri,  5 Jun 2026 07:30:56 +0200 Petr Wozniak wrote:
> commit 8fe125892f40 ("net: phy: sfp: probe for RollBall I2C-to-MDIO
> bridge in mdio-i2c") introduced a regression: the RollBall I2C-to-MDIO
> bridge is not yet ready to respond to CMD_READ/CMD_DONE cycles when
> sfp_sm_add_mdio_bus() runs in SFP_S_INIT.  The 200 ms probe times out,
> i2c_mii_probe_rollball() returns -ENODEV, and sfp_sm_add_mdio_bus()
> sets mdio_protocol = MDIO_I2C_NONE.  By the time sfp_sm_probe_for_phy()
> runs (up to ~17 s later on affected hardware), the bridge is fully
> initialized — but PHY probing is skipped because the protocol has
> already been changed to NONE.
> 
> This affects both modules inserted before boot and hotplugged modules on
> hardware where bridge initialization exceeds the 200 ms probe window
> (confirmed: FLYPRO SFP-10GT-CS-30M with Aquantia AQR113C, hotplugged).
> 
> Move the probe from i2c_mii_init_rollball() — called at bus-creation
> time — to sfp_sm_probe_for_phy() in sfp.c, where it runs after the SFP
> state machine's module initialization delays.  Export the probe function
> as mdio_i2c_probe_rollball() so sfp.c can call it.
> 
> For RTL8261BE-based modules: the probe correctly returns -ENODEV at PHY
> discovery time, causing sfp_sm_probe_for_phy() to destroy the MDIO bus
> and set MDIO_I2C_NONE — eliminating the 5+ minute PHY probe retry loop.
> 
> For genuine RollBall modules (e.g. FLYPRO SFP-10GT-CS-30M with Aquantia
> AQR113C): the probe now runs after initialization is complete and
> correctly returns 0 — PHY detection proceeds normally.

$ git pw series apply 1106341
Failed to apply patch:
Applying: net: phy: mdio-i2c: defer RollBall bridge probe to PHY discovery
error: corrupt patch at .git/rebase-apply/patch:44
error: could not build fake ancestor
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config set advice.mergeConflict false"
Patch failed at 0001 net: phy: mdio-i2c: defer RollBall bridge probe to PHY discovery
-- 
pw-bot: cr


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