BPI-R4 PRO SFP+ link flaps after 1 second link-up

Banana Pi Router design BPI-R4/BPI-R4 Pro(MT7988)
1

Hello, I am testing the 10G SFP+ interface on two Banana Pi BPI-R4-PRO boards from OpenWrt.

Both boards drive 10G CWDM SFP+ modules from OPTCORE, plugged in the SFP-LAN port (mxl_lan5). I have tested multiple modules, including OPC10G-5340DCR and OPC10G-5540DCR, and the behaviour is unchanged.

The optical side both appears healthy, and the green LEDs are on once the fibers are plugged in: Laser output power: +1.58 dBm Receiver signal average optical power: -6.51 dBm

However, the Ethernet link repeatedly flaps. A typical sequence is:

[104327.519713] mxl862xx mdio-bus:10 mxl_lan5: resolve link status: system iface=0 [104327.527034] mxl862xx mdio-bus:10 mxl_lan5: Link is Down [104327.532365] br-lan: port 8(mxl_lan5) entered disabled state [104330.644353] mxl862xx mdio-bus:10 mxl_lan5: resolve link status: system iface=0 (repeated 4x) [104331.679705] mxl862xx mdio-bus:10 mxl_lan5: Link is Up - 10Gbps/Full - flow control off [104331.684378] br-lan: port 8(mxl_lan5) entered blocking state [104331.693350] br-lan: port 8(mxl_lan5) entered forwarding state [104332.729707] mxl862xx mdio-bus:10 mxl_lan5: resolve link status: system iface=0 [104332.737025] mxl862xx mdio-bus:10 mxl_lan5: Link is Down [104332.742352] br-lan: port 8(mxl_lan5) entered disabled state [104475.204355] mxl862xx mdio-bus:10 mxl_lan5: resolve link status: system iface=0 (repeated 138x) [104476.244358] mxl862xx mdio-bus:10 mxl_lan5: Link is Up - 10Gbps/Full - flow control off [104476.249035] br-lan: port 8(mxl_lan5) entered blocking state [104476.258001] br-lan: port 8(mxl_lan5) entered forwarding state [104477.279725] mxl862xx mdio-bus:10 mxl_lan5: resolve link status: system iface=0

This pattern repeats very consistently. The link can briefly enter forwarding, but ARP between the two boards fails and no stable traffic can pass. Also I noticed from the ‘Link is Up’ to ‘Link is Down’ is always an 1 second interval.

One of the board reports carrier=1 in most cases, but the other board always shows carrier=0, though the received power and green LED looks correct.

Has anyone seen this behavior? Are there known firmware, device-tree, SerDes, or driver settings required for stable 10G optical SFP+ operation?

Thanks a lot for the help:)

2

link-up/down issue is known and fixed in openwrt and my repo…which image+kernel do you use?

upstream openwrt (already merged):

in my kernel-repo it is fixed this way:

2fbf4643cdf4 2026-05-06 net: pcs: mtk-usxgmii: check link status and phy ctle before reset Frank Wunderlich 
6dc3a368447e 2026-05-06 phy: mtk-xfi: add mtk_xfi_tphy_valid_ctle for use in usxgmii driver Frank Wunderlich
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Hi Frank thanks a lot for the in-time help. I followed the getting-start to download the image from Banana Pi BPI-R4 Pro Wifi7 Router board design with Mediatek MT7988A | BananaPi Docs, which appears to be:

Linux OpenWrt 6.6.93 #0 SMP Tue Jun 17 03:09:13 2025 aarch64 GNU/Linux

It sounds like the version is out of date? Do we have a prebuilt BPI-R4 image that already includes these fixes, or should I build from current OpenWrt main?

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I have images on my gdrive,but if you want to add own software it is better to compile yourself