ER-X SFP: Howto swconfig/uci set port link speed?

Does anyone have a proper syntax for setting port link speed settings using swconfig or uci?
And, does anyone know whether this should be able to work on a ER-X-(SFP)?

ER-X and ER-X-SFP have a mt7530 switch.
When looking at the swconfig output, it says "unknown" for link parameter:

Attribute 3 (unknown): link (Get port link information)

I checked the driver for mt7530, and as far as I can see it's not implemented to set link options.
Can only find mt7530_get_port_link routine. Major bummer!

Think I'll head over to development forum to see what options are available to set link speed for - in my case - the SFP port to fixed.