linux/drivers/devfreq/Kconfig
MyungJoo Ham ce26c5bb95 PM / devfreq: Add basic governors
Four cpufreq-like governors are provided as examples.

powersave: use the lowest frequency possible. The user (device) should
set the polling_ms as 0 because polling is useless for this governor.

performance: use the highest freqeuncy possible. The user (device)
should set the polling_ms as 0 because polling is useless for this
governor.

userspace: use the user specified frequency stored at
devfreq.user_set_freq. With sysfs support in the following patch, a user
may set the value with the sysfs interface.

simple_ondemand: simplified version of cpufreq's ondemand governor.

When a user updates OPP entries (enable/disable/add), OPP framework
automatically notifies devfreq to update operating frequency
accordingly. Thus, devfreq users (device drivers) do not need to update
devfreq manually with OPP entry updates or set polling_ms for powersave
, performance, userspace, or any other "static" governors.

Note that these are given only as basic examples for governors and any
devices with devfreq may implement their own governors with the drivers
and use them.

Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Mike Turquette <mturquette@ti.com>
Acked-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
2011-10-02 00:19:34 +02:00

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config ARCH_HAS_DEVFREQ
bool
depends on ARCH_HAS_OPP
help
Denotes that the architecture supports DEVFREQ. If the architecture
supports multiple OPP entries per device and the frequency of the
devices with OPPs may be altered dynamically, the architecture
supports DEVFREQ.
menuconfig PM_DEVFREQ
bool "Generic Dynamic Voltage and Frequency Scaling (DVFS) support"
depends on PM_OPP && ARCH_HAS_DEVFREQ
help
With OPP support, a device may have a list of frequencies and
voltages available. DEVFREQ, a generic DVFS framework can be
registered for a device with OPP support in order to let the
governor provided to DEVFREQ choose an operating frequency
based on the OPP's list and the policy given with DEVFREQ.
Each device may have its own governor and policy. DEVFREQ can
reevaluate the device state periodically and/or based on the
OPP list changes (each frequency/voltage pair in OPP may be
disabled or enabled).
Like some CPUs with CPUFREQ, a device may have multiple clocks.
However, because the clock frequencies of a single device are
determined by the single device's state, an instance of DEVFREQ
is attached to a single device and returns a "representative"
clock frequency from the OPP of the device, which is also attached
to a device by 1-to-1. The device registering DEVFREQ takes the
responsiblity to "interpret" the frequency listed in OPP and
to set its every clock accordingly with the "target" callback
given to DEVFREQ.
if PM_DEVFREQ
comment "DEVFREQ Governors"
config DEVFREQ_GOV_SIMPLE_ONDEMAND
bool "Simple Ondemand"
help
Chooses frequency based on the recent load on the device. Works
similar as ONDEMAND governor of CPUFREQ does. A device with
Simple-Ondemand should be able to provide busy/total counter
values that imply the usage rate. A device may provide tuned
values to the governor with data field at devfreq_add_device().
config DEVFREQ_GOV_PERFORMANCE
bool "Performance"
help
Sets the frequency at the maximum available frequency.
This governor always returns UINT_MAX as frequency so that
the DEVFREQ framework returns the highest frequency available
at any time.
config DEVFREQ_GOV_POWERSAVE
bool "Powersave"
help
Sets the frequency at the minimum available frequency.
This governor always returns 0 as frequency so that
the DEVFREQ framework returns the lowest frequency available
at any time.
config DEVFREQ_GOV_USERSPACE
bool "Userspace"
help
Sets the frequency at the user specified one.
This governor returns the user configured frequency if there
has been an input to /sys/devices/.../power/devfreq_set_freq.
Otherwise, the governor does not change the frequnecy
given at the initialization.
comment "DEVFREQ Drivers"
endif # PM_DEVFREQ