Powertop fails with error: “read_msr cpu0 0x3fe : Input/output error” on BYT-M N3540 CPU (model 0x37).

From the sourcecode, it appears c7 support depends on the presence of "/sys/bus/pci/devices/0000:00:13.0" for model 0x37.  Directory "/sys/bus/pci/devices/0000:00:13.0" does not exist on my system.

The commit that introduced this problem is:

commit e01a025bc37f730379edc001e7f12fa269b68fbd

Author: alexandra.yates@linux.intel.com <alexandra.yates@linux.intel.com>

Date:   Fri Aug 22 02:52:19 2014 -0700

    bug fix intel bdw: package c-state support

----

U. Artie