Let’s suppose that we want to add the two governors Smartass and Interactive. Your first step is to locate the required source code for the same class of CPU.

Next, add the source code for the governor. Eg: drivers/cpufreq/cpufreq_interactive.c and drivers/cpufreq/cpufreq_smartass.c

Then add the choice for menuconfig to drivers/cpufreq/Kconfig:

config CPU_FREQ_DEFAULT_GOV_INTERACTIVE

bool "interactive"

select CPU_FREQ_GOV_INTERACTIVE

help

Use the CPUFreq governor 'interactive' as default. This allows

you to get a full dynamic cpu frequency capable system by simply

loading your cpufreq low-level hardware driver, using the

'interactive' governor for latency-sensitive workloads.[/code]


OR


config CPU_FREQ_DEFAULT_GOV_SMARTASS

bool "smartass"

select CPU_FREQ_GOV_SMARTASS

select CPU_FREQ_GOV_PERFORMANCE

help

Use the CPUFreq governor 'smartass' as default.[/code]


and

drivers/cpufreq/Kconfig


config CPU_FREQ_GOV_SMARTASS

tristate "'smartass' cpufreq governor"

depends on CPU_FREQ

help

smartass' - a "smart" optimized governor![/code]


OR


config CPU_FREQ_GOV_SMARTASS2

tristate "'smartass2' cpufreq policy governor"

help

'smartassV2' - a "smart" governor[/code]


 


If in doubt, say N.


Then, the rules to compile the source code, in Makefile


obj-$(CONFIG_CPU_FREQ_GOV_SMARTASS) += cpufreq_smartass.o[/code]


Then, the definitions in the header file include/linux/cpufreq.h


#elif defined(CONFIG_CPU_FREQ_DEFAULT_GOV_SMARTASS)[/code]


extern struct cpufreq_governor cpufreq_gov_smartass;


#define CPUFREQ_DEFAULT_GOVERNOR (&cpufreq_gov_smartass)


 


After adding these, dont forget to enable them in CPU Power Management tab of menuconfig

While compiling, check whether the .o file for the particular freq is being made. Otherwise, it may mean you have forgotten to add the rules in the drivers/cpufreq/Kconfig file


Enabling HAVS:

Dont forget:

System type:

QSD Static Voltage Scaling

PMIC default output voltage

Enable Adaptive Voltage Scaling (AVS)


How does it work?


driver/cpufreq/Kconfig contains menuitems for adding to .config. Based on the selection of these items when menuconfig is done, at build it looks for these rules within the header files located in include/linux/cpufreq.h


include/linux/cpufreq.h


/*********************************************************************

 *                       CPUFREQ DEFAULT GOVERNOR                    *

 *********************************************************************/


/*

  Performance governor is fallback governor if any other gov failed to

  auto load due latency restrictions

*/

#ifdef CONFIG_CPU_FREQ_GOV_PERFORMANCE

extern struct cpufreq_governor cpufreq_gov_performance;

#endif

#ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE

#define CPUFREQ_DEFAULT_GOVERNOR	(&cpufreq_gov_performance)

#elif defined(CONFIG_CPU_FREQ_DEFAULT_GOV_POWERSAVE)

extern struct cpufreq_governor cpufreq_gov_powersave;

#define CPUFREQ_DEFAULT_GOVERNOR	(&cpufreq_gov_powersave)

#elif defined(CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE)

extern struct cpufreq_governor cpufreq_gov_userspace;

#define CPUFREQ_DEFAULT_GOVERNOR	(&cpufreq_gov_userspace)

#elif defined(CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND)

extern struct cpufreq_governor cpufreq_gov_ondemand;

#define CPUFREQ_DEFAULT_GOVERNOR	(&cpufreq_gov_ondemand)

#elif defined(CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE)

extern struct cpufreq_governor cpufreq_gov_conservative;

#define CPUFREQ_DEFAULT_GOVERNOR	(&cpufreq_gov_conservative)

#elif defined(CONFIG_CPU_FREQ_DEFAULT_GOV_INTERACTIVE)

extern struct cpufreq_governor cpufreq_gov_interactive;

#define CPUFREQ_DEFAULT_GOVERNOR	(&cpufreq_gov_interactive)

#endif[/code]


drivers/cpufreq/Kconfig


config CPU_FREQ

	bool "CPU Frequency scaling"

	help

	  CPU Frequency scaling allows you to change the clock speed of

	  CPUs on the fly. This is a nice method to save power, because

	  the lower the CPU clock speed, the less power the CPU consumes.


	  Note that this driver doesn't automatically change the CPU

	  clock speed, you need to either enable a dynamic cpufreq governor

	  (see below) after boot, or use a userspace tool.


	  For details, take a look at .


	  If in doubt, say N.


if CPU_FREQ


config CPU_FREQ_TABLE

	tristate


config CPU_FREQ_DEBUG

	bool "Enable CPUfreq debugging"

	help

	  Say Y here to enable CPUfreq subsystem (including drivers)

	  debugging. You will need to activate it via the kernel

	  command line by passing

	     cpufreq.debug=


	  To get , add

	       1 to activate CPUfreq core debugging,

	       2 to activate CPUfreq drivers debugging, and

	       4 to activate CPUfreq governor debugging


config CPU_FREQ_STAT

	tristate "CPU frequency translation statistics"

	select CPU_FREQ_TABLE

	default y

	help

	  This driver exports CPU frequency statistics information through sysfs

	  file system.


	  To compile this driver as a module, choose M here: the

	  module will be called cpufreq_stats.


	  If in doubt, say N.


config CPU_FREQ_STAT_DETAILS

	bool "CPU frequency translation statistics details"

	depends on CPU_FREQ_STAT

	help

	  This will show detail CPU frequency translation table in sysfs file

	  system.


	  If in doubt, say N.


choice

	prompt "Default CPUFreq governor"

	default CPU_FREQ_DEFAULT_GOV_USERSPACE if CPU_FREQ_SA1100 || CPU_FREQ_SA1110

	default CPU_FREQ_DEFAULT_GOV_PERFORMANCE

	help

	  This option sets which CPUFreq governor shall be loaded at

	  startup. If in doubt, select 'performance'.


config CPU_FREQ_DEFAULT_GOV_PERFORMANCE

	bool "performance"

	select CPU_FREQ_GOV_PERFORMANCE

	help

	  Use the CPUFreq governor 'performance' as default. This sets

	  the frequency statically to the highest frequency supported by

	  the CPU.


config CPU_FREQ_DEFAULT_GOV_POWERSAVE

	bool "powersave"

	depends on EMBEDDED

	select CPU_FREQ_GOV_POWERSAVE

	help

	  Use the CPUFreq governor 'powersave' as default. This sets

	  the frequency statically to the lowest frequency supported by

	  the CPU.


config CPU_FREQ_DEFAULT_GOV_USERSPACE

	bool "userspace"

	select CPU_FREQ_GOV_USERSPACE

	help

	  Use the CPUFreq governor 'userspace' as default. This allows

	  you to set the CPU frequency manually or when a userspace

	  program shall be able to set the CPU dynamically without having

	  to enable the userspace governor manually.


config CPU_FREQ_DEFAULT_GOV_ONDEMAND

	bool "ondemand"

	select CPU_FREQ_GOV_ONDEMAND

	select CPU_FREQ_GOV_PERFORMANCE

	help

	  Use the CPUFreq governor 'ondemand' as default. This allows

	  you to get a full dynamic frequency capable system by simply

	  loading your cpufreq low-level hardware driver.

	  Be aware that not all cpufreq drivers support the ondemand

	  governor. If unsure have a look at the help section of the

	  driver. Fallback governor will be the performance governor.


config CPU_FREQ_DEFAULT_GOV_CONSERVATIVE

	bool "conservative"

	select CPU_FREQ_GOV_CONSERVATIVE

	select CPU_FREQ_GOV_PERFORMANCE

	help

	  Use the CPUFreq governor 'conservative' as default. This allows

	  you to get a full dynamic frequency capable system by simply

	  loading your cpufreq low-level hardware driver.

	  Be aware that not all cpufreq drivers support the conservative

	  governor. If unsure have a look at the help section of the

	  driver. Fallback governor will be the performance governor.


config CPU_FREQ_DEFAULT_GOV_INTERACTIVE

	bool "interactive"

	select CPU_FREQ_GOV_INTERACTIVE

	help

	  Use the CPUFreq governor 'interactive' as default. This allows

	  you to get a full dynamic cpu frequency capable system by simply

	  loading your cpufreq low-level hardware driver, using the

	  'interactive' governor for latency-sensitive workloads.


config CPU_FREQ_DEFAULT_GOV_SMARTASS2

	bool "smartass2"

	select CPU_FREQ_GOV_SMARTASS2

	help

	  Use the CPUFreq governor 'smartass2' as default. This allows

	  you to get a full dynamic cpu frequency capable system by simply

	  loading your cpufreq low-level hardware driver, using the

	  'interactive' governor for latency-sensitive workloads.


endchoice


config CPU_FREQ_GOV_PERFORMANCE

	tristate "'performance' governor"

	help

	  This cpufreq governor sets the frequency statically to the

	  highest available CPU frequency.


	  To compile this driver as a module, choose M here: the

	  module will be called cpufreq_performance.


	  If in doubt, say Y.


config CPU_FREQ_GOV_POWERSAVE

	tristate "'powersave' governor"

	help

	  This cpufreq governor sets the frequency statically to the

	  lowest available CPU frequency.


	  To compile this driver as a module, choose M here: the

	  module will be called cpufreq_powersave.


	  If in doubt, say Y.


config CPU_FREQ_GOV_USERSPACE

	tristate "'userspace' governor for userspace frequency scaling"

	help

	  Enable this cpufreq governor when you either want to set the

	  CPU frequency manually or when a userspace program shall

	  be able to set the CPU dynamically, like on LART

	  .


	  To compile this driver as a module, choose M here: the

	  module will be called cpufreq_userspace.


	  For details, take a look at .


	  If in doubt, say Y.


config CPU_FREQ_GOV_ONDEMAND

	tristate "'ondemand' cpufreq policy governor"

	select CPU_FREQ_TABLE

	help

	  'ondemand' - This driver adds a dynamic cpufreq policy governor.

	  The governor does a periodic polling and

	  changes frequency based on the CPU utilization.

	  The support for this governor depends on CPU capability to

	  do fast frequency switching (i.e, very low latency frequency

	  transitions). 


	  To compile this driver as a module, choose M here: the

	  module will be called cpufreq_ondemand.


	  For details, take a look at linux/Documentation/cpu-freq.


	  If in doubt, say N.


config CPU_FREQ_GOV_INTERACTIVE

	tristate "'interactive' cpufreq policy governor"

	help

	  'interactive' - This driver adds a dynamic cpufreq policy governor

	  designed for latency-sensitive workloads.


config CPU_FREQ_GOV_SMARTASS2

	tristate "'smartass2' cpufreq policy governor"

	help

	  'smartassV2' - a "smart" governor


config CPU_FREQ_GOV_CONSERVATIVE

	tristate "'conservative' cpufreq governor"

	depends on CPU_FREQ

	help

	  'conservative' - this driver is rather similar to the 'ondemand'

	  governor both in its source code and its purpose, the difference is

	  its optimisation for better suitability in a battery powered

	  environment.  The frequency is gracefully increased and decreased

	  rather than jumping to 100% when speed is required.


	  If you have a desktop machine then you should really be considering

	  the 'ondemand' governor instead, however if you are using a laptop,

	  PDA or even an AMD64 based computer (due to the unacceptable

	  step-by-step latency issues between the minimum and maximum frequency

	  transitions in the CPU) you will probably want to use this governor.


	  To compile this driver as a module, choose M here: the

	  module will be called cpufreq_conservative.


	  For details, take a look at linux/Documentation/cpu-freq.


	  If in doubt, say N.

config CPU_FREQ_MIN_TICKS

	int "Ticks between governor polling interval."

	default 10

	help

	  Minimum number of ticks between polling interval for governors.


config CPU_FREQ_SAMPLING_LATENCY_MULTIPLIER

	int "Sampling rate multiplier for governors."

	default 1000

	help

	  Sampling latency rate multiplied by the cpu switch latency.

	  Affects governor polling.


config CPU_FREQ_VDD_LEVELS

	bool "CPU Vdd levels sysfs interface"

	depends on CPU_FREQ_STAT

	depends on ARCH_QSD8X50

	default n

	help

	  CPU Vdd levels sysfs interface


endif	# CPU_FREQ[/code]


More notes:


/*

 * Notes by Droidzone

 *

 * General format for adding governors

 * -----------------------------------

 *

 * ifdef/elif Condition as per value in drivers/cpufreq/Kconfig

 *

 * CPUFREQ_DEFAULT_GOVERNOR is the variable pointing to the default governor

 *

 * Reads: if configured some governor as default, then define the governor

 * by an object

 *

 * Thus: extern struc cpufreq_governor cpufreq_gov_interactive

 * is pointed here.. the target is in cpufreq_interactive.c, the specific

 * code in cpufreq/

 *

 * [extern struct cpufreq_governor] followed by the name as defined in its

 * source code:

 *

 * Eg In cpufreq_smartass2.c is this:

 * struct cpufreq_governor cpufreq_gov_smartass2 = {

 . name = "smartassV2",                 *

 .governor = cpufreq_governor_smartass,

 *

 *

 */

#ifdef CONFIG_CPU_FREQ_GOV_PERFORMANCE

extern struct cpufreq_governor cpufreq_gov_performance;

#endif

#ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE

#define CPUFREQ_DEFAULT_GOVERNOR	(&cpufreq_gov_performance)

#elif defined(CONFIG_CPU_FREQ_DEFAULT_GOV_POWERSAVE)

extern struct cpufreq_governor cpufreq_gov_powersave;

#define CPUFREQ_DEFAULT_GOVERNOR	(&cpufreq_gov_powersave)

#elif defined(CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE)

extern struct cpufreq_governor cpufreq_gov_userspace;

#define CPUFREQ_DEFAULT_GOVERNOR	(&cpufreq_gov_userspace)

#elif defined(CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND)

extern struct cpufreq_governor cpufreq_gov_ondemand;

#define CPUFREQ_DEFAULT_GOVERNOR	(&cpufreq_gov_ondemand)

#elif defined(CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE)

extern struct cpufreq_governor cpufreq_gov_conservative;

#define CPUFREQ_DEFAULT_GOVERNOR	(&cpufreq_gov_conservative)

#elif defined(CONFIG_CPU_FREQ_DEFAULT_GOV_INTERACTIVE)

extern struct cpufreq_governor cpufreq_gov_interactive;

#define CPUFREQ_DEFAULT_GOVERNOR	(&cpufreq_gov_interactive)

#elif defined(CONFIG_CPU_FREQ_DEFAULT_GOV_SMARTASS2)

extern struct cpufreq_governor cpufreq_gov_smartass2;

#define CPUFREQ_DEFAULT_GOVERNOR	(&cpufreq_gov_smartass2)

#endif[/code]