How can I enable the deep RC6 sleep states on an haswell architecture?

Question

If you use iotopyou will see three sleep states. One is called RC6 and the other two are deep sleep states called RC6p and RC6pp. I read the modinfo i915 and saw that one can enable them by passing enable_rc6=7 to the kernel.

parm: enable_rc6:Enable power-saving render C-state 6. Different stages can be selected via bitmask values (0 = disable; 1 = enable rc6; 2 = enable deep rc6; 4 = enable deepest rc6). For example, 3 would enable rc6 and deep rc6, and 7 would enable everything. default: -1 (use per-chip default) (int)

But after a reboot I recognized that only RC6 is enabled. I passed this param via the kernel command line and via modprobe.d, but non of them worked. So how can I enable these deep states?

Answer 1

The simple answer is you can't. Those sleep states have been abandoned, since the haswell architecture. There is only RC6 left. See here or here.