RE: [PATCH net-next] r8169: add quirk for RTL8116af SerDes

[Hau <hau@realtek.com>]

> On Mon, Jul 14, 2025 at 03:28:37PM +0000, Hau wrote:
> > >
> > > Can you give us a few more details. What is on the other end of the
> SERDES?
> > > An SGMII PHY? An SFP cage? An Ethernet switch chip?
> > >
> > > A quick search suggests it is used with an SFP cage. How is the I2C
> > > bus connected? What about GPIOs? Does the RTL8116af itself have
> > > GPIOs and an I2C bus?
> > >
> 
> > RTL8116af 's SERDES will connect to a SFP cage. It has GPIO and a I2C
> > bus. But driver did not use it to access SFP cage.  Driver depends on
> > mac io 0x6c (LinkStatus) to check link status.
> 
> You cannot correctly use an SFP cage without using the I2C bus and the
> GPIOs. e.g. A copper SFP module likely needs SGMII, where as a fibre
> module needs 1000BaseX. You need to reprogram the PCS depending on
> what the SFP EEPROM says.
> 
> The kernel has all the code needed to coordinate this, phylink. All you need
> to do is write a standard Linux I2C bus driver, a standard Linux GPIO driver,
> and turn your PCS into a Linux PCS. You can then instantiate an SFP device.
> The txgbe driver does this, you can probably copy the code from there.
> 
> Have you licensed these parts? The txgbe hardware uses synopsys I2C and
> PCS. So all that was needed was a wrapper around the existing drivers.
> 
Thanks for your advice. I will check this internally to see if we can do this on device.

Thanks.