Same for FX5200.
It seems there does not exist any support yet.
I have looked into the matter, but the first thing I encountered is that the Nvidia driver keeps the I2C buses locked in some way, and that there is no public interface to the I2C routines in that driver.
So, additionally loaded driver modules cannot access the I2C bus. This somewhat rules out the possibility of writing something that co-operates with the Nvidia driver.
When I experiment with X not running, I can access the I2C but the chip on my card is not supported by rivatv, and the chip maker has sent me a datasheet that does not include I2C register programming info.
So there are several problems to solve...
I think I can get a better datasheet when I keep trying, but I doubt I can get any response from Nvidia discussing driver issues. The Nvidia people have not posted on this forum for many months :-(