Ghoul Sorcerer Bloodline - Ravenous Frenzy

[Oncoming_Storm]

Howdy Pathfinders. I can't quite understand how the haste aspect of this ability works. There doesn't seem to be an action cost or anything, and that doesn't seem right. Hoping you could help clear things up.

Ravenous Frenzy (Ex) At 9th level, you gain the benefits of haste for a number of rounds per day equal to your sorcerer level. These rounds don't need to be consecutive. Each time you hit a creature with two or more claw attacks during a full attack while affected by this ability, that creature takes 1d4 points of bleed damage.

Here's the bloodline in full.

[Cavall]

I can't see the point of an activation cost to haste. Since its measured in rounds this seems fair.