netdev - [PATCH net-next] r8169: bail out from probe if fiber mode is detected on RTL8127AF

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Message-ID: <fab6605a-54e2-4f54-b194-11c2b9caaaa9@gmail.com>
Date: Thu, 13 Nov 2025 22:09:08 +0100
From: Heiner Kallweit <hkallweit1@...il.com>
To: Realtek linux nic maintainers <nic_swsd@...ltek.com>,
 Andrew Lunn <andrew+netdev@...n.ch>, Paolo Abeni <pabeni@...hat.com>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Simon Horman <horms@...nel.org>
Cc: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
 Daniel Golle <daniel@...rotopia.org>
Subject: [PATCH net-next] r8169: bail out from probe if fiber mode is detected
 on RTL8127AF

It was reported that on a card with RTL8127AF (SFP + DAC) link-up isn't
detected. Realtek hides the SFP behind the internal PHY, which isn't
behaving fully compliance with clause 22 any longer in fiber mode.
Due to not having access to chip documentation there isn't much I can
do for now. Instead of silently failing to detect link-up in fiber mode,
inform the user that fiber mode isn't support and bail out.

The logic to detect fiber mode is borrowed from Realtek's r8127 driver.

Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
---
 drivers/net/ethernet/realtek/r8169_main.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
index 2a4d9b548..d9113b6c6 100644
--- a/drivers/net/ethernet/realtek/r8169_main.c
+++ b/drivers/net/ethernet/realtek/r8169_main.c
@@ -5448,6 +5448,15 @@ static int rtl_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 	}
 	tp->aspm_manageable = !rc;
 
+	/* Fiber mode on RTL8127AF isn't supported */
+	if (rtl_is_8125(tp)) {
+		u16 data = r8168_mac_ocp_read(tp, 0xd006);
+
+		if ((data & 0xff) == 0x07)
+			return dev_err_probe(&pdev->dev, -ENODEV,
+					     "Fiber mode not supported\n");
+	}
+
 	tp->dash_type = rtl_get_dash_type(tp);
 	tp->dash_enabled = rtl_dash_is_enabled(tp);
 
-- 
2.51.2