In the early days of Nouveau, lots of data dumps were needed for reverse-engineering the NVIDIA binary blob. Basically MMIOtrace was loaded to the kernel (the support was since mainlined) and to then trace the driver's interaction with the graphics hardware during various operations. Not as many of these data dumps are needed these days for existing hardware since the Nouveau developers generally have a rather good understanding of how to program the NVIDIA graphics processors.
Nouveau contributor Roy Spliet is calling out today for more NVIDIA MMIOtrace dumps for certain GPUs. He's in need of more MMIotraces on NVIDIA NVAA and NVAF GPUs, which comes down to GeForce 8 series mobile GPUs, GeForce 9 series mobile GPUs, NVIDIA ION, and the nForce IGP. He's wanting this data from different NVIDIA GPus to try to better understand the NVAC clock tree.
Roy made the call for this data on the Nouveau mailing list. Collecting NVIDIA MMIOtraces really aren't a hard process for non-developer Linux users. If you need to understand the collection process better, see the Nouveau Wiki and the Ubuntu X tracing guide.