PMU Engine Counter Support For Nouveau, Needed For Dynamic Reclocking

Karol Herbst has published a set of patches for implementing PMU engine counters, which will be needed for supporting dynamic re-clocking with newer GPUs.

Herbst explained with his new patch series that the PMU engine counters are needed for dynamic re-clocking with the GT215 (GeForce GT 240) and newer. These engine counters are used for getting the core, memory, video, and PCI Express loads. Based upon the load information, the Nouveau driver can then make better assumptions about whether to increase/decrease the various frequencies of the hardware.

This patch series though doesn't do the actual wiring up of any dynamic re-clocking. With this counter support, the data is currently then just exposed via debugfs. For now, Nouveau just supports disabled-by-default, manual, static re-clocking until all the core/vRAM re-clocking issues are sorted through.

This code adds more than 2,500 lines of new code (and adjusts around one thousand other lines). Hopefully this code is in good shape and the PMU engine counters support can be merged then into Linux 4.6. It's great as well seeing Karol becoming one of the most prolific, independent contributors to Nouveau when it comes to re-clocking support.