Re: [PATCH net-next v5] r8169: add support for rtl8168h(revid 0x2a) + rtl8211fs fiber application

[Heiner Kallweit <hkallweit1@gmail.com>]

On 12.12.2022 15:11, Hau wrote:
>> On 09.12.2022 16:29, Hau wrote:
>>>>
>>>> OK, I think I get a better idea of your setup.
>>>> So it seems RTL8211FS indeed acts as media converter. Link status on
>>>> MDI side of RTL8211FS reflects link status on fiber/serdes side.
>>>> RTL8168H PHY has no idea whether it's connected to RJ45 magnetics or
>>>> to the MDI side of a RTL8211FS.
>>>>
>>>> I think for configuring RTL8211FS you have two options:
>>>> 1. Extend the Realtek PHY driver to support RTL8211FS fiber mode 2.
>>>> Configure RTL8211FS from userspace (phytool, mii-tool, ..). However
>>>> to be able to do this you may need to add a dummy netdevice
>>>>    that RTL8211FS is attached to. When going with this option it may
>>>> be better to avoid phylib taking control of RTL8211FS.
>>>>    This can be done by setting the phy_mask of the bit-banged mii_bus.
>>>
>>> Thanks for your advaice.
>>> Is that possible for us to register a PHY fixup function(phy_register_fixup())
>> to setup rtl8211fs instead of setup it in PHY driver?
>>>
>> From where would you like to register the PHY fixup? r8169 would be the
>> wrong place here.
>> There are very few drivers using a PHY fixup and AFAICS typically PHY drivers
>> apply fixups from the config_init callback.
>> Having said that, if possible I'd recommend to avoid using a PHY fixup.
>>
> Thanks for your prompt reply. I think in next patch I will remove the rtl8211fs phy parameter setting.
> And only keep non speed down patch.
> If there's any possibility I'd like to avoid the non speed down patch.
You would have to think also about the case that a user uses ethtool
to restrict advertisement to 100Mbps, what would break the connection.
r8169 isn't the right place for a workaround for a broken media converter.
The media converter should be fully transparent to r8169.

RTL8211FS should align the advertisement on MDI side with the link
speed on fiber side, based on SGMII in-band information.
If the fiber link is 1Gbps it must not advertise 100Mbps on MDI side.