I don't know for certain what "Voltage Swing" does, but after I changed it from 0 to 1 I can use a 3m Display Port cable.
FWIW, I'm using:
- 1 x AMD FirePro W7000, driver version 17.Q2.1
- 3 x Samsung U28D590 (4k)
Up until this change, I'd been unable to use anything other than a 2m Display Port cable. So thanks AMD as now my PC can sit under the desk :-) Happy days...
These options can potentially help a user overcome intermittent flashing or black screen issues that sometimes occur with monitors due to a bug or firmware issue.