Re: [PATCH] net: sfp: add quirks for GPON ONT SFP sticks

[John Pavlick]

  Thank you for the review.

  You are correct that the commit message was inaccurate — the Banana Pi R3 / MT7986 SerDes is not fixed at 2500base-X and does support 1000base-X and SGMII as well. I apologize for the
  misleading description. I will send a v3 with a corrected commit message.

  Regarding the concern about breaking 1G support on boards that do not support 2500base-X: sfp_quirk_2500basex only adds 2500base-X to the module's advertised capabilities via
  linkmode_set_bit — it does not remove the 1000BASE-LX capability reported by the EEPROM. The kernel should still be able to negotiate 1G on boards that do not support 2500base-X. That
  said, I do not have access to older MikroTik QCA9xxx-based hardware to test this, so I welcome any additional guidance.

> On 6 Apr 2026, at 14:48, Daniel Golle <daniel@xxxxxxxxxxxxxx> wrote:
> 
> On Mon, Apr 06, 2026 at 11:44:05AM +0000, John Pavlick wrote:
>> Several GPON ONT SFP sticks based on Realtek RTL960x report
>> 1000BASE-LX at 1300MBd in their EEPROM but can operate at 2500base-X.
>> On hosts with serdes fixed at 2.5Gbase-X (e.g. Banana Pi R3 / MT7986),
>> the kernel rejects them with 'no common interface modes'.
> 
> While the quirks themselves may be correct, the statement above is wrong.
> The BananaPi R3 (and all MediaTek router SoCs) *do* support also
> 1000Base-X and SGMII, the SerDes is *not* "fixed at 2.5GBase-X". This
> can easily be verified by plugging a random 1Gbps SFP module into the
> board (eg. ubiquitous copper modules based on Marvell 88E1111 PHY).
> 
> Also you have to make sure to not break support for those modules on
> boards which do not support 2500Base-X and need the module to operate
> at 1000Base-X (eg. older MikroTik QCA9xxx-based MIPS boards).