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executable file 40 lines (37 sloc) 1.32 KB
#!/bin/sh
#title: c6off+c7on.sh
#description: Disables all C6 and enables all C7 core states for Baytrail CPUs
#author: Wolfgang Reimer <linuxball (at) gmail.com>
#date: 2016014
#version: 1.0
#usage: sudo <path>/c6off+c7on.sh
#notes: Intended as test script to verify whether erratum VLP52 (see
# [1]) is the root cause for kernel bug 109051 (see [2]). In order
# for this to work you must _NOT_ use boot parameter
# intel_idle.max_cstate=<number>.
#
# [1] http://www.intel.com/content/dam/www/public/us/en/documents/specification-updates/pentium-n3520-j2850-celeron-n2920-n2820-n2815-n2806-j1850-j1750-spec-update.pdf
# [2] https://bugzilla.kernel.org/show_bug.cgi?id=109051
# Disable ($1 == 1) or enable ($1 == 0) core state, if not yet done.
disable() {
local action
read disabled <disable
test "$disabled" = $1 && return
echo $1 >disable || return
action=ENABLED; test "$1" = 0 || action=DISABLED
printf "%-8s state %7s for %s.\n" $action "$name" $cpu
}
# Iterate through each core state and for Baytrail (BYT) disable all C6
# and enable all C7 states.
cd /sys/devices/system/cpu
for cpu in cpu[0-9]*; do
for dir in $cpu/cpuidle/state*; do
cd "$dir"
read name <name
case $name in
C6*) disable 1;;
C7*) disable 0;;
esac
cd ../../..
done
done