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cpuidle: improve governor Kconfig options

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Each governor is suitable for different kernel configurations: the menu
governor suits better for a tickless system, while the ladder governor fits
better for a periodic timer tick system.

The Kconfig does not allow to [un]select a governor, thus both are compiled in
the kernel but the init order makes the menu governor to be the last one to be
registered, so becoming the default. The only way to switch back to the ladder
governor is to enable the sysfs governor switch in the kernel command line.

Because it seems nobody complained about this, the menu governor is used by
default most of the time on the system, having both governors is not really
necessary on a tickless system but there isn't a config option to disable one
or another governor.

Create a submenu for cpuidle and add a label for each governor, so we can see
the option in the menu config and enable/disable it.

The governors will be enabled depending on the CONFIG_NO_HZ option:
 - If CONFIG_NO_HZ is set, then the menu governor is selected and the ladder
   governor is optional, defaulting to 'yes'
 - If CONFIG_NO_HZ is not set, then the ladder governor is selected and the
   menu governor is optional, defaulting to 'yes'

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Daniel Lezcano 2013-05-28 15:51:54 +00:00 committed by Rafael J. Wysocki
parent d683b96b07
commit d6f346f2d2
1 changed files with 7 additions and 9 deletions
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16
drivers/cpuidle/Kconfig
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@ -1,7 +1,9 @@
config CPU_IDLE
menuconfig CPU_IDLE
bool "CPU idle PM support"
default y if ACPI || PPC_PSERIES
select CPU_IDLE_GOV_LADDER if (!NO_HZ && !NO_HZ_IDLE)
select CPU_IDLE_GOV_MENU if (NO_HZ || NO_HZ_IDLE)
help
CPU idle is a generic framework for supporting software-controlled
idle processor power management. It includes modular cross-platform
@ -9,9 +11,10 @@ config CPU_IDLE
If you're using an ACPI-enabled platform, you should say Y here.
if CPU_IDLE
config CPU_IDLE_MULTIPLE_DRIVERS
bool "Support multiple cpuidle drivers"
depends on CPU_IDLE
default n
help
Allows the cpuidle framework to use different drivers for each CPU.
@ -19,24 +22,19 @@ config CPU_IDLE_MULTIPLE_DRIVERS
states. If unsure say N.
config CPU_IDLE_GOV_LADDER
bool
depends on CPU_IDLE
bool "Ladder governor (for periodic timer tick)"
default y
config CPU_IDLE_GOV_MENU
bool
depends on CPU_IDLE && NO_HZ
bool "Menu governor (for tickless system)"
default y
config ARCH_NEEDS_CPU_IDLE_COUPLED
def_bool n
if CPU_IDLE
config CPU_IDLE_CALXEDA
bool "CPU Idle Driver for Calxeda processors"
depends on ARCH_HIGHBANK
help
Select this to enable cpuidle on Calxeda processors.
endif