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(a)linux.intel.com <alexandra.yates(a)linux.intel.com>
Date: Fri Aug 22 02:52:19 2014 -0700
bug fix intel bdw: package c-state support
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U. Artie