--- zzzz-none-000/linux-3.10.107/Documentation/cpu-freq/cpu-drivers.txt 2017-06-27 09:49:32.000000000 +0000 +++ scorpion-7490-727/linux-3.10.107/Documentation/cpu-freq/cpu-drivers.txt 2021-02-04 17:41:59.000000000 +0000 @@ -23,9 +23,10 @@ 1.1 Initialization 1.2 Per-CPU Initialization 1.3 verify -1.4 target or setpolicy? -1.5 target +1.4 target/target_index or setpolicy? +1.5 target/target_index 1.6 setpolicy +1.7 get_intermediate and target_intermediate 2. Frequency Table Helpers @@ -50,30 +51,39 @@ cpufreq_driver.name - The name of this driver. -cpufreq_driver.owner - THIS_MODULE; - cpufreq_driver.init - A pointer to the per-CPU initialization function. cpufreq_driver.verify - A pointer to a "verification" function. cpufreq_driver.setpolicy _or_ -cpufreq_driver.target - See below on the differences. +cpufreq_driver.target/ +target_index - See below on the differences. And optionally -cpufreq_driver.exit - A pointer to a per-CPU cleanup function. +cpufreq_driver.exit - A pointer to a per-CPU cleanup + function called during CPU_POST_DEAD + phase of cpu hotplug process. + +cpufreq_driver.stop_cpu - A pointer to a per-CPU stop function + called during CPU_DOWN_PREPARE phase of + cpu hotplug process. cpufreq_driver.resume - A pointer to a per-CPU resume function which is called with interrupts disabled and _before_ the pre-suspend frequency and/or policy is restored by a call to - ->target or ->setpolicy. + ->target/target_index or ->setpolicy. cpufreq_driver.attr - A pointer to a NULL-terminated list of "struct freq_attr" which allow to export values to sysfs. +cpufreq_driver.get_intermediate +and target_intermediate Used to switch to stable frequency while + changing CPU frequency. + 1.2 Per-CPU Initialization -------------------------- @@ -105,8 +115,8 @@ this CPU. A few moments later, cpufreq_driver.verify and either cpufreq_driver.setpolicy or - cpufreq_driver.target is called with - these values. + cpufreq_driver.target/target_index is called + with these values. For setting some of these values (cpuinfo.min[max]_freq, policy->min[max]), the frequency table helpers might be helpful. See the section 2 for more information @@ -135,20 +145,31 @@ policy->max first, and only if this is no solution, decrease policy->min. -1.4 target or setpolicy? +1.4 target/target_index or setpolicy? ---------------------------- Most cpufreq drivers or even most cpu frequency scaling algorithms only allow the CPU to be set to one frequency. For these, you use the -->target call. +->target/target_index call. Some cpufreq-capable processors switch the frequency between certain limits on their own. These shall use the ->setpolicy call -1.4. target +1.5. target/target_index ------------- +The target_index call has two arguments: struct cpufreq_policy *policy, +and unsigned int index (into the exposed frequency table). + +The CPUfreq driver must set the new frequency when called here. The +actual frequency must be determined by freq_table[index].frequency. + +It should always restore to earlier frequency (i.e. policy->restore_freq) in +case of errors, even if we switched to intermediate frequency earlier. + +Deprecated: +---------- The target call has three arguments: struct cpufreq_policy *policy, unsigned int target_frequency, unsigned int relation. @@ -166,7 +187,7 @@ for details. -1.5 setpolicy +1.6 setpolicy --------------- The setpolicy call only takes a struct cpufreq_policy *policy as @@ -177,6 +198,23 @@ powersaving-oriented setting when CPUFREQ_POLICY_POWERSAVE. Also check the reference implementation in drivers/cpufreq/longrun.c +1.7 get_intermediate and target_intermediate +-------------------------------------------- + +Only for drivers with target_index() and CPUFREQ_ASYNC_NOTIFICATION unset. + +get_intermediate should return a stable intermediate frequency platform wants to +switch to, and target_intermediate() should set CPU to to that frequency, before +jumping to the frequency corresponding to 'index'. Core will take care of +sending notifications and driver doesn't have to handle them in +target_intermediate() or target_index(). + +Drivers can return '0' from get_intermediate() in case they don't wish to switch +to intermediate frequency for some target frequency. In that case core will +directly call ->target_index(). + +NOTE: ->target_index() should restore to policy->restore_freq in case of +failures as core would send notifications for that. 2. Frequency Table Helpers @@ -186,7 +224,7 @@ frequencies, a "frequency table" with some functions might assist in some work of the processor driver. Such a "frequency table" consists of an array of struct cpufreq_frequency_table entries, with any value in -"index" you want to use, and the corresponding frequency in +"driver_data" you want to use, and the corresponding frequency in "frequency". At the end of the table, you need to add a cpufreq_frequency_table entry with frequency set to CPUFREQ_TABLE_END. And if you want to skip one entry in the table, set the frequency to @@ -214,10 +252,23 @@ is the corresponding frequency table helper for the ->target stage. Just pass the values to this function, and the unsigned int index returns the number of the frequency table entry which contains -the frequency the CPU shall be set to. PLEASE NOTE: This is not the -"index" which is in this cpufreq_table_entry.index, but instead -cpufreq_table[index]. So, the new frequency is -cpufreq_table[index].frequency, and the value you stored into the -frequency table "index" field is -cpufreq_table[index].index. +the frequency the CPU shall be set to. + +The following macros can be used as iterators over cpufreq_frequency_table: + +cpufreq_for_each_entry(pos, table) - iterates over all entries of frequency +table. + +cpufreq-for_each_valid_entry(pos, table) - iterates over all entries, +excluding CPUFREQ_ENTRY_INVALID frequencies. +Use arguments "pos" - a cpufreq_frequency_table * as a loop cursor and +"table" - the cpufreq_frequency_table * you want to iterate over. + +For example: + + struct cpufreq_frequency_table *pos, *driver_freq_table; + cpufreq_for_each_entry(pos, driver_freq_table) { + /* Do something with pos */ + pos->frequency = ... + }