[PATCH net v4 2/2] net: phy: mdio-i2c: defer RollBall bridge probe to PHY discovery
Aleksander Jan Bajkowski
olek2 at wp.pl
Wed Jun 24 14:44:19 PDT 2026
Hi Petr,
W dniu 24.06.2026 o 10:48, Petr Wozniak pisze:
> 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 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, so PHY detection proceeds normally.
The FLPRO SFP module still fails to detect the PHY. It is necessary to
increase `module_t_wait` to 20 seconds. Most likely, during this time
the module loads the PHY firmware from SPI memory or from the
microcontroller (rollball bridge) via MDIO. Same probably applies to
most SFP modules with a PHY that load firmware at start-up (AQR113,
RTL8261C etc.).
>
> Reported-by: Aleksander Bajkowski <olek2 at wp.pl>
> Fixes: 8fe125892f40 ("net: phy: sfp: probe for RollBall I2C-to-MDIO bridge in mdio-i2c")
> Signed-off-by: Petr Wozniak <petr.wozniak at gmail.com>
> ---
> drivers/net/mdio/mdio-i2c.c | 15 +++++++++------
> drivers/net/phy/sfp.c | 22 ++++++++++++++--------
> include/linux/mdio/mdio-i2c.h | 1 +
> 3 files changed, 24 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/net/mdio/mdio-i2c.c b/drivers/net/mdio/mdio-i2c.c
> index b88f63234b4e..2a3a418c1369 100644
> --- a/drivers/net/mdio/mdio-i2c.c
> +++ b/drivers/net/mdio/mdio-i2c.c
> @@ -419,7 +419,7 @@ static int i2c_mii_write_rollball(struct mii_bus *bus, int phy_id, int devad,
> return 0;
> }
>
> -static int i2c_mii_probe_rollball(struct i2c_adapter *i2c)
> +int mdio_i2c_probe_rollball(struct i2c_adapter *i2c)
> {
> u8 data_buf[] = { ROLLBALL_DATA_ADDR, 0x01, 0x00, 0x00 };
> u8 cmd_buf[] = { ROLLBALL_CMD_ADDR, ROLLBALL_CMD_READ };
> @@ -462,9 +462,13 @@ static int i2c_mii_probe_rollball(struct i2c_adapter *i2c)
>
> return -ENODEV;
> }
> +EXPORT_SYMBOL_GPL(mdio_i2c_probe_rollball);
>
> static int i2c_mii_init_rollball(struct i2c_adapter *i2c)
> {
> + /* Send the RollBall unlock password; bridge presence is verified
> + * later, in sfp_sm_probe_for_phy(), after module initialization.
> + */
> struct i2c_msg msg;
> u8 pw[5];
> int ret;
> @@ -486,7 +490,7 @@ static int i2c_mii_init_rollball(struct i2c_adapter *i2c)
> if (ret != 1)
> return -EIO;
>
> - return i2c_mii_probe_rollball(i2c);
> + return 0;
> }
>
> static bool mdio_i2c_check_functionality(struct i2c_adapter *i2c,
> @@ -531,10 +535,9 @@ struct mii_bus *mdio_i2c_alloc(struct device *parent, struct i2c_adapter *i2c,
> case MDIO_I2C_ROLLBALL:
> ret = i2c_mii_init_rollball(i2c);
> if (ret < 0) {
> - if (ret != -ENODEV)
> - dev_err(parent,
> - "Cannot initialize RollBall MDIO I2C protocol: %d\n",
> - ret);
> + dev_err(parent,
> + "Cannot initialize RollBall MDIO I2C protocol: %d\n",
> + ret);
> mdiobus_free(mii);
> return ERR_PTR(ret);
> }
> diff --git a/drivers/net/phy/sfp.c b/drivers/net/phy/sfp.c
> index c4d274ab651e..01b941a38eed 100644
> --- a/drivers/net/phy/sfp.c
> +++ b/drivers/net/phy/sfp.c
> @@ -2174,17 +2174,10 @@ static void sfp_sm_fault(struct sfp *sfp, unsigned int next_state, bool warn)
>
> static int sfp_sm_add_mdio_bus(struct sfp *sfp)
> {
> - int ret;
> -
> if (sfp->mdio_protocol == MDIO_I2C_NONE)
> return 0;
>
> - ret = sfp_i2c_mdiobus_create(sfp);
> - if (ret == -ENODEV) {
> - sfp->mdio_protocol = MDIO_I2C_NONE;
> - return 0;
> - }
> - return ret;
> + return sfp_i2c_mdiobus_create(sfp);
> }
>
> /* Probe a SFP for a PHY device if the module supports copper - the PHY
> @@ -2215,6 +2208,19 @@ static int sfp_sm_probe_for_phy(struct sfp *sfp)
> break;
>
> case MDIO_I2C_ROLLBALL:
> + /* Probe here, after module initialization delays, so that
> + * genuine RollBall bridges have had time to start up.
> + * Modules without a bridge (e.g. RTL8261BE) return -ENODEV.
> + */
> + err = mdio_i2c_probe_rollball(sfp->i2c);
> + if (err == -ENODEV) {
> + sfp_i2c_mdiobus_destroy(sfp);
> + sfp->mdio_protocol = MDIO_I2C_NONE;
> + err = 0;
> + break;
> + }
> + if (err)
> + break;
> err = sfp_sm_probe_phy(sfp, SFP_PHY_ADDR_ROLLBALL, true);
> break;
> }
> diff --git a/include/linux/mdio/mdio-i2c.h b/include/linux/mdio/mdio-i2c.h
> index 65b550a6fc32..5cf14f45c94b 100644
> --- a/include/linux/mdio/mdio-i2c.h
> +++ b/include/linux/mdio/mdio-i2c.h
> @@ -20,5 +20,6 @@ enum mdio_i2c_proto {
>
> struct mii_bus *mdio_i2c_alloc(struct device *parent, struct i2c_adapter *i2c,
> enum mdio_i2c_proto protocol);
> +int mdio_i2c_probe_rollball(struct i2c_adapter *i2c);
>
> #endif
Best regards,
Aleksander
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