Something

[root@localhost C000]# cat power 
active state:            C1
max_cstate:              C8
bus master activity:     00180001
maximum allowed latency: 2000 usec
states:
   *C1:                  type[C1] promotion[C3] demotion[--] latency[000] usage[00324441] duration[00000000000000000000]
    C2:                  <not supported>
    C3:                  type[C3] promotion[--] demotion[C1] latency[010] usage[00000074] duration[00000000000002201642]