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

[Petr Wozniak]

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.

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@xxxxx>
Suggested-by: Maxime Chevallier <maxime.chevallier@xxxxxxxxxxx>
Link: https://lore.kernel.org/netdev/20260624084814.20972-1-petr.wozniak@xxxxxxxxx/
Signed-off-by: Petr Wozniak <petr.wozniak@xxxxxxxxx>
---
 drivers/net/mdio/mdio-i2c.c | 59 +++++--------------------------------
 drivers/net/phy/sfp.c       | 14 ++-------
 2 files changed, 10 insertions(+), 63 deletions(-)

diff --git a/drivers/net/mdio/mdio-i2c.c b/drivers/net/mdio/mdio-i2c.c
index b88f63234b4e..ed20352a589a 100644
--- a/drivers/net/mdio/mdio-i2c.c
+++ b/drivers/net/mdio/mdio-i2c.c
@@ -419,50 +419,6 @@ 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)
-{
-	u8 data_buf[] = { ROLLBALL_DATA_ADDR, 0x01, 0x00, 0x00 };
-	u8 cmd_buf[]  = { ROLLBALL_CMD_ADDR, ROLLBALL_CMD_READ };
-	u8 cmd_addr   = ROLLBALL_CMD_ADDR;
-	struct i2c_msg msgs[2];
-	u8 result;
-	int ret;
-	int i;
-
-	msgs[0].addr  = ROLLBALL_PHY_I2C_ADDR;
-	msgs[0].flags = 0;
-	msgs[0].len   = sizeof(data_buf);
-	msgs[0].buf   = data_buf;
-	msgs[1].addr  = ROLLBALL_PHY_I2C_ADDR;
-	msgs[1].flags = 0;
-	msgs[1].len   = sizeof(cmd_buf);
-	msgs[1].buf   = cmd_buf;
-
-	ret = i2c_transfer_rollball(i2c, msgs, ARRAY_SIZE(msgs));
-	if (ret < 0)
-		return -ENODEV;
-
-	msgs[0].addr  = ROLLBALL_PHY_I2C_ADDR;
-	msgs[0].flags = 0;
-	msgs[0].len   = 1;
-	msgs[0].buf   = &cmd_addr;
-	msgs[1].addr  = ROLLBALL_PHY_I2C_ADDR;
-	msgs[1].flags = I2C_M_RD;
-	msgs[1].len   = 1;
-	msgs[1].buf   = &result;
-
-	for (i = 0; i < 10; i++) {
-		msleep(20);
-		ret = i2c_transfer_rollball(i2c, msgs, ARRAY_SIZE(msgs));
-		if (ret < 0)
-			return -ENODEV;
-		if (result == ROLLBALL_CMD_DONE)
-			return 0;
-	}
-
-	return -ENODEV;
-}
-
 static int i2c_mii_init_rollball(struct i2c_adapter *i2c)
 {
 	struct i2c_msg msg;
@@ -482,11 +438,11 @@ static int i2c_mii_init_rollball(struct i2c_adapter *i2c)
 
 	ret = i2c_transfer(i2c, &msg, 1);
 	if (ret < 0)
-		return -ENODEV;
-	if (ret != 1)
+		return ret;
+	else if (ret != 1)
 		return -EIO;
-
-	return i2c_mii_probe_rollball(i2c);
+	else
+		return 0;
 }
 
 static bool mdio_i2c_check_functionality(struct i2c_adapter *i2c,
@@ -531,10 +487,9 @@ 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..f520206734da 100644
--- a/drivers/net/phy/sfp.c
+++ b/drivers/net/phy/sfp.c
@@ -597,7 +597,6 @@ static const struct sfp_quirk sfp_quirks[] = {
 	// OEM SFP-GE-T is a 1000Base-T module with broken TX_FAULT indicator
 	SFP_QUIRK_F("OEM", "SFP-GE-T", sfp_fixup_ignore_tx_fault),
 
-	SFP_QUIRK_F("OEM", "SFP-10G-T-I", sfp_fixup_rollball),
 	SFP_QUIRK_F("OEM", "SFP-10G-T", sfp_fixup_rollball_cc),
 	SFP_QUIRK_S("OEM", "SFP-2.5G-T", sfp_quirk_oem_2_5g),
 	SFP_QUIRK_S("OEM", "SFP-2.5G-BX10-D", sfp_quirk_2500basex),
@@ -2174,17 +2173,10 @@ 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;
+	if (sfp->mdio_protocol != MDIO_I2C_NONE)
+		return sfp_i2c_mdiobus_create(sfp);
 
-	ret = sfp_i2c_mdiobus_create(sfp);
-	if (ret == -ENODEV) {
-		sfp->mdio_protocol = MDIO_I2C_NONE;
-		return 0;
-	}
-	return ret;
+	return 0;
 }
 
 /* Probe a SFP for a PHY device if the module supports copper - the PHY
-- 
2.51.0