OPP library provides a set of helper functions to organize and query the OPP
information. The library is located in drivers/base/power/opp.c and the header
OPP library provides a set of helper functions to organize and query the OPP
information. The library is located in drivers/base/power/opp.c and the header
CONFIG_PM_OPP from power management menuconfig menu. OPP library depends on
CONFIG_PM as certain SoCs such as Texas Instrument's OMAP framework allows to
optionally boot at a certain OPP without needing cpufreq.
CONFIG_PM_OPP from power management menuconfig menu. OPP library depends on
CONFIG_PM as certain SoCs such as Texas Instrument's OMAP framework allows to
optionally boot at a certain OPP without needing cpufreq.
OPP library facilitates this concept in it's implementation. The following
operational functions operate only on available opps:
OPP library facilitates this concept in it's implementation. The following
operational functions operate only on available opps:
-opp_find_freq_{ceil, floor}, opp_get_voltage, opp_get_freq, opp_get_opp_count
-and opp_init_cpufreq_table
+opp_find_freq_{ceil, floor}, dev_pm_opp_get_voltage, dev_pm_opp_get_freq, dev_pm_opp_get_opp_count
+and dev_pm_opp_init_cpufreq_table
-opp_find_freq_exact is meant to be used to find the opp pointer which can then
-be used for opp_enable/disable functions to make an opp available as required.
+dev_pm_opp_find_freq_exact is meant to be used to find the opp pointer which can then
+be used for dev_pm_opp_enable/disable functions to make an opp available as required.
exact mechanism to trigger these or the notification mechanism to other
dependent subsystems such as cpufreq are left to the discretion of the SoC
specific framework which uses the OPP library. Similar care needs to be taken
exact mechanism to trigger these or the notification mechanism to other
dependent subsystems such as cpufreq are left to the discretion of the SoC
specific framework which uses the OPP library. Similar care needs to be taken
opp_get_{voltage, freq, opp_count} fall into this category.
opp_{add,enable,disable} are updaters which use mutex and implement it's own
opp_get_{voltage, freq, opp_count} fall into this category.
opp_{add,enable,disable} are updaters which use mutex and implement it's own
mutex to implment RCU updater strategy. These functions should *NOT* be called
under RCU locks and other contexts that prevent blocking functions in RCU or
mutex operations from working.
2. Initial OPP List Registration
================================
mutex to implment RCU updater strategy. These functions should *NOT* be called
under RCU locks and other contexts that prevent blocking functions in RCU or
mutex operations from working.
2. Initial OPP List Registration
================================
device. It is expected that the SoC framework will register the OPP entries
optimally- typical numbers range to be less than 5. The list generated by
registering the OPPs is maintained by OPP library throughout the device
operation. The SoC framework can subsequently control the availability of the
device. It is expected that the SoC framework will register the OPP entries
optimally- typical numbers range to be less than 5. The list generated by
registering the OPPs is maintained by OPP library throughout the device
operation. The SoC framework can subsequently control the availability of the
The OPP is defined using the frequency and voltage. Once added, the OPP
is assumed to be available and control of it's availability can be done
The OPP is defined using the frequency and voltage. Once added, the OPP
is assumed to be available and control of it's availability can be done
and manages this information in the opp struct. This function may be
used by SoC framework to define a optimal list as per the demands of
SoC usage environment.
and manages this information in the opp struct. This function may be
used by SoC framework to define a optimal list as per the demands of
SoC usage environment.
found, else returns error. These errors are expected to be handled by standard
error checks such as IS_ERR() and appropriate actions taken by the caller.
found, else returns error. These errors are expected to be handled by standard
error checks such as IS_ERR() and appropriate actions taken by the caller.
availability. This function is especially useful to enable an OPP which
is not available by default.
Example: In a case when SoC framework detects a situation where a
higher frequency could be made available, it can use this function to
availability. This function is especially useful to enable an OPP which
is not available by default.
Example: In a case when SoC framework detects a situation where a
higher frequency could be made available, it can use this function to
rcu_read_unlock();
/* dont operate on the pointer.. just do a sanity check.. */
if (IS_ERR(opp)) {
pr_err("frequency not disabled!\n");
/* trigger appropriate actions.. */
} else {
rcu_read_unlock();
/* dont operate on the pointer.. just do a sanity check.. */
if (IS_ERR(opp)) {
pr_err("frequency not disabled!\n");
/* trigger appropriate actions.. */
} else {
provided frequency. This function is useful while searching for a lesser
match OR operating on OPP information in the order of decreasing
frequency.
Example: To find the highest opp for a device:
freq = ULONG_MAX;
rcu_read_lock();
provided frequency. This function is useful while searching for a lesser
match OR operating on OPP information in the order of decreasing
frequency.
Example: To find the highest opp for a device:
freq = ULONG_MAX;
rcu_read_lock();
provided frequency. This function is useful while searching for a
higher match OR operating on OPP information in the order of increasing
frequency.
Example 1: To find the lowest opp for a device:
freq = 0;
rcu_read_lock();
provided frequency. This function is useful while searching for a
higher match OR operating on OPP information in the order of increasing
frequency.
Example 1: To find the lowest opp for a device:
freq = 0;
rcu_read_lock();
Example: Lets say that 1GHz OPP is to be made available only if the
SoC temperature is lower than a certain threshold. The SoC framework
implementation might choose to do something as follows:
if (cur_temp < temp_low_thresh) {
/* Enable 1GHz if it was disabled */
rcu_read_lock();
Example: Lets say that 1GHz OPP is to be made available only if the
SoC temperature is lower than a certain threshold. The SoC framework
implementation might choose to do something as follows:
if (cur_temp < temp_low_thresh) {
/* Enable 1GHz if it was disabled */
rcu_read_lock();
Example: Lets say that 1GHz OPP is to be disabled if the temperature
exceeds a threshold value. The SoC framework implementation might
choose to do something as follows:
if (cur_temp > temp_high_thresh) {
/* Disable 1GHz if it was enabled */
rcu_read_lock();
Example: Lets say that 1GHz OPP is to be disabled if the temperature
exceeds a threshold value. The SoC framework implementation might
choose to do something as follows:
if (cur_temp > temp_high_thresh) {
/* Disable 1GHz if it was enabled */
rcu_read_lock();
retrieved using the search functions, the following functions can be used by SoC
framework to retrieve the information represented inside the OPP layer.
retrieved using the search functions, the following functions can be used by SoC
framework to retrieve the information represented inside the OPP layer.
Example: At a cpufreq transition to a different frequency, SoC
framework requires to set the voltage represented by the OPP using
the regulator framework to the Power Management chip providing the
Example: At a cpufreq transition to a different frequency, SoC
framework requires to set the voltage represented by the OPP using
the regulator framework to the Power Management chip providing the
- opp = opp_find_freq_ceil(dev, &freq);
- v = opp_get_voltage(opp);
+ opp = dev_pm_opp_find_freq_ceil(dev, &freq);
+ v = dev_pm_opp_get_voltage(opp);
Example: Lets say the SoC framework uses a couple of helper functions
we could pass opp pointers instead of doing additional parameters to
handle quiet a bit of data parameters.
Example: Lets say the SoC framework uses a couple of helper functions
we could pass opp pointers instead of doing additional parameters to
handle quiet a bit of data parameters.
- max_opp = opp_find_freq_floor(dev,&max_freq);
- requested_opp = opp_find_freq_ceil(dev,&freq);
+ max_opp = dev_pm_opp_find_freq_floor(dev,&max_freq);
+ requested_opp = dev_pm_opp_find_freq_ceil(dev,&freq);
if (!IS_ERR(max_opp) && !IS_ERR(requested_opp))
r = soc_test_validity(max_opp, requested_opp);
rcu_read_unlock();
if (!IS_ERR(max_opp) && !IS_ERR(requested_opp))
r = soc_test_validity(max_opp, requested_opp);
rcu_read_unlock();
Example: Lets say a co-processor in the SoC needs to know the available
frequencies in a table, the main processor can notify as following:
soc_notify_coproc_available_frequencies()
{
/* Do things */
rcu_read_lock();
Example: Lets say a co-processor in the SoC needs to know the available
frequencies in a table, the main processor can notify as following:
soc_notify_coproc_available_frequencies()
{
/* Do things */
rcu_read_lock();
speeds = kzalloc(sizeof(u32) * num_available, GFP_KERNEL);
/* populate the table in increasing order */
freq = 0;
speeds = kzalloc(sizeof(u32) * num_available, GFP_KERNEL);
/* populate the table in increasing order */
freq = 0;
cpufreq_frequency_table_cpuinfo which is provided with the list of
frequencies that are available for operation. This function provides
a ready to use conversion routine to translate the OPP layer's internal
cpufreq_frequency_table_cpuinfo which is provided with the list of
frequencies that are available for operation. This function provides
a ready to use conversion routine to translate the OPP layer's internal
addition to CONFIG_PM as power management feature is required to
dynamically scale voltage and frequency in a system.
addition to CONFIG_PM as power management feature is required to
dynamically scale voltage and frequency in a system.
representing the actual OPPs and domains are internal to the OPP library itself
to allow for suitable abstraction reusable across systems.
representing the actual OPPs and domains are internal to the OPP library itself
to allow for suitable abstraction reusable across systems.
represent an OPP. In addition to the freq, voltage, availability
information, it also contains internal book keeping information required
for the OPP library to operate on. Pointer to this structure is
provided back to the users such as SoC framework to be used as a
identifier for OPP in the interactions with OPP layer.
represent an OPP. In addition to the freq, voltage, availability
information, it also contains internal book keeping information required
for the OPP library to operate on. Pointer to this structure is
provided back to the users such as SoC framework to be used as a
identifier for OPP in the interactions with OPP layer.
- WARNING: The struct opp pointer should not be parsed or modified by the
- users. The defaults of for an instance is populated by opp_add, but the
- availability of the OPP can be modified by opp_enable/disable functions.
+ WARNING: The struct dev_pm_opp pointer should not be parsed or modified by the
+ users. The defaults of for an instance is populated by dev_pm_opp_add, but the
+ availability of the OPP can be modified by dev_pm_opp_enable/disable functions.
struct device - This is used to identify a domain to the OPP layer. The
nature of the device and it's implementation is left to the user of
struct device - This is used to identify a domain to the OPP layer. The
nature of the device and it's implementation is left to the user of
- +-----+ /- opp_enable
-opp_add --> | opp | <-------
- | +-----+ \- opp_disable
+ +-----+ /- dev_pm_opp_enable
+dev_pm_opp_add --> | opp | <-------
+ | +-----+ \- dev_pm_opp_disable
- /-- opp_find_freq_ceil ---\ +-----+
-domain_info<---- opp_find_freq_exact -----> | opp |
- \-- opp_find_freq_floor ---/ +-----+
+ /-- dev_pm_opp_find_freq_ceil ---\ +-----+
+domain_info<---- dev_pm_opp_find_freq_exact -----> | opp |
+ \-- dev_pm_opp_find_freq_floor ---/ +-----+