diff options
Diffstat (limited to 'Documentation/power/opp.txt')
| -rw-r--r-- | Documentation/power/opp.txt | 108 |
1 files changed, 54 insertions, 54 deletions
diff --git a/Documentation/power/opp.txt b/Documentation/power/opp.txt index 425c51d56aef..b8a907dc0169 100644 --- a/Documentation/power/opp.txt +++ b/Documentation/power/opp.txt @@ -42,7 +42,7 @@ We can represent these as three OPPs as the following {Hz, uV} tuples: 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 -is located in include/linux/opp.h. OPP library can be enabled by enabling +is located in include/linux/pm_opp.h. OPP library can be enabled by enabling 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. @@ -71,14 +71,14 @@ operations until that OPP could be re-enabled if possible. 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. WARNING: Users of OPP library should refresh their availability count using -get_opp_count if opp_enable/disable functions are invoked for a device, the +get_opp_count if dev_pm_opp_enable/disable functions are invoked for a device, the 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 @@ -96,24 +96,24 @@ using RCU read locks. The opp_find_freq_{exact,ceil,floor}, opp_get_{voltage, freq, opp_count} fall into this category. opp_{add,enable,disable} are updaters which use mutex and implement it's own -RCU locking mechanisms. opp_init_cpufreq_table acts as an updater and uses +RCU locking mechanisms. dev_pm_opp_init_cpufreq_table acts as an updater and uses 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 ================================ -The SoC implementation calls opp_add function iteratively to add OPPs per +The SoC implementation calls dev_pm_opp_add function iteratively to add OPPs per 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 -OPPs dynamically using the opp_enable / disable functions. +OPPs dynamically using the dev_pm_opp_enable / disable functions. -opp_add - Add a new OPP for a specific domain represented by the device pointer. +dev_pm_opp_add - Add a new OPP for a specific domain represented by the device pointer. 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 - with the opp_enable/disable functions. OPP library internally stores + with the dev_pm_opp_enable/disable functions. OPP library internally stores 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. @@ -124,7 +124,7 @@ opp_add - Add a new OPP for a specific domain represented by the device pointer. soc_pm_init() { /* Do things */ - r = opp_add(mpu_dev, 1000000, 900000); + r = dev_pm_opp_add(mpu_dev, 1000000, 900000); if (!r) { pr_err("%s: unable to register mpu opp(%d)\n", r); goto no_cpufreq; @@ -143,44 +143,44 @@ functions return the matching pointer representing the opp if a match is 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. -opp_find_freq_exact - Search for an OPP based on an *exact* frequency and +dev_pm_opp_find_freq_exact - Search for an OPP based on an *exact* frequency and 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 - find the OPP prior to call the opp_enable to actually make it available. + find the OPP prior to call the dev_pm_opp_enable to actually make it available. rcu_read_lock(); - opp = opp_find_freq_exact(dev, 1000000000, false); + opp = dev_pm_opp_find_freq_exact(dev, 1000000000, false); 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 { - opp_enable(dev,1000000000); + dev_pm_opp_enable(dev,1000000000); } NOTE: This is the only search function that operates on OPPs which are not available. -opp_find_freq_floor - Search for an available OPP which is *at most* the +dev_pm_opp_find_freq_floor - Search for an available OPP which is *at most* the 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(); - opp_find_freq_floor(dev, &freq); + dev_pm_opp_find_freq_floor(dev, &freq); rcu_read_unlock(); -opp_find_freq_ceil - Search for an available OPP which is *at least* the +dev_pm_opp_find_freq_ceil - Search for an available OPP which is *at least* the 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(); - opp_find_freq_ceil(dev, &freq); + dev_pm_opp_find_freq_ceil(dev, &freq); rcu_read_unlock(); Example 2: A simplified implementation of a SoC cpufreq_driver->target: soc_cpufreq_target(..) @@ -188,7 +188,7 @@ opp_find_freq_ceil - Search for an available OPP which is *at least* the /* Do stuff like policy checks etc. */ /* Find the best frequency match for the req */ rcu_read_lock(); - opp = opp_find_freq_ceil(dev, &freq); + opp = dev_pm_opp_find_freq_ceil(dev, &freq); rcu_read_unlock(); if (!IS_ERR(opp)) soc_switch_to_freq_voltage(freq); @@ -208,34 +208,34 @@ as thermal considerations (e.g. don't use OPPx until the temperature drops). WARNING: Do not use these functions in interrupt context. -opp_enable - Make a OPP available for operation. +dev_pm_opp_enable - Make a OPP available for operation. 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(); - opp = opp_find_freq_exact(dev, 1000000000, false); + opp = dev_pm_opp_find_freq_exact(dev, 1000000000, false); rcu_read_unlock(); /* just error check */ if (!IS_ERR(opp)) - ret = opp_enable(dev, 1000000000); + ret = dev_pm_opp_enable(dev, 1000000000); else goto try_something_else; } -opp_disable - Make an OPP to be not available for operation +dev_pm_opp_disable - Make an OPP to be not available for operation 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(); - opp = opp_find_freq_exact(dev, 1000000000, true); + opp = dev_pm_opp_find_freq_exact(dev, 1000000000, true); rcu_read_unlock(); /* just error check */ if (!IS_ERR(opp)) - ret = opp_disable(dev, 1000000000); + ret = dev_pm_opp_disable(dev, 1000000000); else goto try_something_else; } @@ -247,7 +247,7 @@ information from the OPP structure is necessary. Once an OPP pointer is retrieved using the search functions, the following functions can be used by SoC framework to retrieve the information represented inside the OPP layer. -opp_get_voltage - Retrieve the voltage represented by the opp pointer. +dev_pm_opp_get_voltage - Retrieve the voltage represented by the opp pointer. 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 @@ -256,15 +256,15 @@ opp_get_voltage - Retrieve the voltage represented by the opp pointer. { /* do things */ rcu_read_lock(); - 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); rcu_read_unlock(); if (v) regulator_set_voltage(.., v); /* do other things */ } -opp_get_freq - Retrieve the freq represented by the opp pointer. +dev_pm_opp_get_freq - Retrieve the freq represented by the opp pointer. 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. @@ -273,8 +273,8 @@ opp_get_freq - Retrieve the freq represented by the opp pointer. /* do things.. */ max_freq = ULONG_MAX; rcu_read_lock(); - 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(); @@ -282,25 +282,25 @@ opp_get_freq - Retrieve the freq represented by the opp pointer. } soc_test_validity(..) { - if(opp_get_voltage(max_opp) < opp_get_voltage(requested_opp)) + if(dev_pm_opp_get_voltage(max_opp) < dev_pm_opp_get_voltage(requested_opp)) return -EINVAL; - if(opp_get_freq(max_opp) < opp_get_freq(requested_opp)) + if(dev_pm_opp_get_freq(max_opp) < dev_pm_opp_get_freq(requested_opp)) return -EINVAL; /* do things.. */ } -opp_get_opp_count - Retrieve the number of available opps for a device +dev_pm_opp_get_opp_count - Retrieve the number of available opps for a device 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(); - num_available = opp_get_opp_count(dev); + num_available = dev_pm_opp_get_opp_count(dev); speeds = kzalloc(sizeof(u32) * num_available, GFP_KERNEL); /* populate the table in increasing order */ freq = 0; - while (!IS_ERR(opp = opp_find_freq_ceil(dev, &freq))) { + while (!IS_ERR(opp = dev_pm_opp_find_freq_ceil(dev, &freq))) { speeds[i] = freq; freq++; i++; @@ -313,7 +313,7 @@ opp_get_opp_count - Retrieve the number of available opps for a device 6. Cpufreq Table Generation =========================== -opp_init_cpufreq_table - cpufreq framework typically is initialized with +dev_pm_opp_init_cpufreq_table - cpufreq framework typically is initialized with 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 @@ -326,7 +326,7 @@ opp_init_cpufreq_table - cpufreq framework typically is initialized with soc_pm_init() { /* Do things */ - r = opp_init_cpufreq_table(dev, &freq_table); + r = dev_pm_opp_init_cpufreq_table(dev, &freq_table); if (!r) cpufreq_frequency_table_cpuinfo(policy, freq_table); /* Do other things */ @@ -336,7 +336,7 @@ opp_init_cpufreq_table - cpufreq framework typically is initialized with addition to CONFIG_PM as power management feature is required to dynamically scale voltage and frequency in a system. -opp_free_cpufreq_table - Free up the table allocated by opp_init_cpufreq_table +dev_pm_opp_free_cpufreq_table - Free up the table allocated by dev_pm_opp_init_cpufreq_table 7. Data Structures ================== @@ -358,16 +358,16 @@ accessed by various functions as described above. However, the structures representing the actual OPPs and domains are internal to the OPP library itself to allow for suitable abstraction reusable across systems. -struct opp - The internal data structure of OPP library which is used to +struct dev_pm_opp - The internal data structure of OPP library which is used to 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 @@ -377,19 +377,19 @@ Overall, in a simplistic view, the data structure operations is represented as following: Initialization / modification: - +-----+ /- opp_enable -opp_add --> | opp | <------- - | +-----+ \- opp_disable + +-----+ /- dev_pm_opp_enable +dev_pm_opp_add --> | opp | <------- + | +-----+ \- dev_pm_opp_disable \-------> domain_info(device) Search functions: - /-- 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 ---/ +-----+ Retrieval functions: -+-----+ /- opp_get_voltage ++-----+ /- dev_pm_opp_get_voltage | opp | <--- -+-----+ \- opp_get_freq ++-----+ \- dev_pm_opp_get_freq -domain_info <- opp_get_opp_count +domain_info <- dev_pm_opp_get_opp_count |