From: Carsten Emde Date: Thu, 19 Jul 2012 20:34:10 +0000 (+0000) Subject: Honor state disabling in the cpuidle ladder governor X-Git-Tag: omap-for-v3.7-rc1/fixes-cpufreq-signed~39^2~11^2~4 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=62d6ae880e3e76098d5e345decd2dce443975889;p=pandora-kernel.git Honor state disabling in the cpuidle ladder governor There are two cpuidle governors ladder and menu. While the ladder governor is always available, if CONFIG_CPU_IDLE is selected, the menu governor additionally requires CONFIG_NO_HZ. A particular C state can be disabled by writing to the sysfs file /sys/devices/system/cpu/cpuN/cpuidle/stateN/disable, but this mechanism is only implemented in the menu governor. Thus, in a system where CONFIG_NO_HZ is not selected, the ladder governor becomes default and always will walk through all sleep states - irrespective of whether the C state was disabled via sysfs or not. The only way to select a specific C state was to write the related latency to /dev/cpu_dma_latency and keep the file open as long as this setting was required - not very practical and not suitable for setting a single core in an SMP system. With this patch, the ladder governor only will promote to the next C state, if it has not been disabled, and it will demote, if the current C state was disabled. Note that the patch does not make the setting of the sysfs variable "disable" coherent, i.e. if one is disabling a light state, then all deeper states are disabled as well, but the "disable" variable does not reflect it. Likewise, if one enables a deep state but a lighter state still is disabled, then this has no effect. A related section has been added to the documentation. Signed-off-by: Carsten Emde Signed-off-by: Rafael J. Wysocki --- Reading git-diff-tree failed