AMD just hasn't made a driver that can do this, why? Because there isn't a gamer market for linux I am betting they didn't see the cost effectiveness of programming one for a market that is unlikely to use their product for anything other than academic/trasncoding in the first place.

Like I said before, just use RadeonBiosEditor under windows to set the values, THEN you can put it in a linux machine and have everything preclocked/tweaked requiring with no extra drivers or tweaking at all.