Nouveau does not suspend my discrete GPU if idle. However bbswitch (nouveau unloaded) is capable to suspend the GPU. I am running the 4.9.24 linux kernel.
My GPU: NVIDIA Corporation GM204M [GeForce GTX 970M] (rev ff)
Nouveau was capable to switch off the discrete GPU until kernel 4.7.
Starting with 4.8 it stopped working.
Hope we can get this fixed. Thanks!
Can you try booting with pcie_pm_port=off ? If this helps, this may be an instance of bug 98398.