quoted

Hi Florian

I didn't need anything like this for the mv88e6xxx. I had patches
merged in -rc1 to make SFF work connected to the mv88e6390. The DT
change was not merged, but it is here:

https://patchwork.ozlabs.org/patch/955635/

+					port@9 {
+						reg = <9>;
+						label = "sff2";
+						phy-mode = "sgmii";
+						managed = "in-band-status";

						^=====

Yes that is what I was missing, thanks Andrew! Still not 100% sure why
having a "sfp" phandle is not enough, but I suppose there are
problematic cases like the ZII Devel Rev. B where we have a SFF and we
are not able to auto-negotiate the fiber connection.

ZII Devel Rev. B is actually broken, should not work, but does
somehow. The SFF 3 and 4 are connected to switch ports which cannot do
1000Base-X. They are using something like SGMII. So the link partner
needs to be very forgiving. But it happens that the link partners i'm
testing against are forgiving. SFF 1 and 2 are generally not
populated. If they are, i think you need to remove a resistor, to make
them work. But they are then connected to a switch port which does use
1000Base-X.

Now, since ZII devel B is technically broken, i would not be too
unhappy if "sfp" phandle implies managed = "in-band-status" by
default, so long as we can still use fixed-link somehow.

	 Andrew