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>

1 files changed, 36 insertions, 0 deletions

diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
index 1fb42de4f420..643b055ed3cd 100644
--- a/drivers/devfreq/Kconfig
+++ b/drivers/devfreq/Kconfig
@@ -34,6 +34,42 @@ menuconfig PM_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