Convert core file to ReST format, in order to allow it to be parsed by Sphinx. Make a minor change of correcting the wrong function name cpufreq_put_cpu to cpufreq_cpu_put. Also create an index.rst file in cpu-freq and add it's entry in the main Documentation/index.rst file. Signed-off-by: Shreeya Patel <shreeya.patel23498@xxxxxxxxx> --- Documentation/cpu-freq/core.rst | 114 +++++++++++++++++++++++++++++ Documentation/cpu-freq/core.txt | 120 ------------------------------- Documentation/cpu-freq/index.rst | 14 ++++ Documentation/index.rst | 1 + 4 files changed, 129 insertions(+), 120 deletions(-) create mode 100644 Documentation/cpu-freq/core.rst delete mode 100644 Documentation/cpu-freq/core.txt create mode 100644 Documentation/cpu-freq/index.rst diff --git a/Documentation/cpu-freq/core.rst b/Documentation/cpu-freq/core.rst new file mode 100644 index 000000000000..b4cf48633797 --- /dev/null +++ b/Documentation/cpu-freq/core.rst @@ -0,0 +1,114 @@ +.. SPDX-License-Identifier: GPL-2.0 + +CPUFreq Core +============ + +Authors: + +- Dominik Brodowski <linux@xxxxxxxx>, +- David Kimdon <dwhedon@xxxxxxxxxx>, +- Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>, +- Viresh Kumar <viresh.kumar@xxxxxxxxxx> + + +Clock scaling allows you to change the clock speed of the CPUs on the +fly. This is a nice method to save battery power, because the lower +the clock speed, the less power the CPU consumes. + + +1. General Information +---------------------- + +The CPUFreq core code is located in :file:`drivers/cpufreq/cpufreq.c`. This +cpufreq code offers a standardized interface for the CPUFreq +architecture drivers (those pieces of code that do actual +frequency transitions), as well as to "notifiers". These are device +drivers or other part of the kernel that need to be informed of +policy changes (ex. thermal modules like ACPI) or of all +frequency changes (ex. timing code) or even need to force certain +speed limits (like LCD drivers on ARM architecture). Additionally, the +kernel "constant" :c:data:`loops_per_jiffy` is updated on frequency changes +here. + +Reference counting of the cpufreq policies is done by :c:func:`cpufreq_cpu_put` +and :c:func:`cpufreq_cpu_put`, which make sure that the cpufreq driver is +correctly registered with the core, and will not be unloaded until +:c:func:`cpufreq_cpu_put` is called. That also ensures that the respective cpufreq +policy doesn't get freed while being used. + +2. CPUFreq notifiers +-------------------- + +CPUFreq notifiers conform to the standard kernel notifier interface. +See :file:`linux/include/linux/notifier.h` for details on notifiers. + +There are two different CPUFreq notifiers - policy notifiers and +transition notifiers. + + +2.1 CPUFreq policy notifiers +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +These are notified when a new policy is intended to be set. Each +CPUFreq policy notifier is called twice for a policy transition: + + 1) During :c:macro:`CPUFREQ_ADJUST` all CPUFreq notifiers may change + the limit if they see a need for this - may it be thermal considerations + or hardware limitations. + + 2) And during :c:macro:`CPUFREQ_NOTIFY` all notifiers are informed of the + new policy - if two hardware drivers failed to agree on a new policy + before this stage, the incompatible hardware shall be shut down, and the user + informed of this. + +The phase is specified in the second argument to the notifier. + +The third argument, a :c:data:`void *pointer`, points to a :c:type:`struct cpufreq_policy` +consisting of several values, including min, max (the lower and upper +frequencies (in kHz) of the new policy). + + +2.2 CPUFreq transition notifiers +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +These are notified twice for each online CPU in the policy, when the +CPUfreq driver switches the CPU core frequency and this change has no +any external implications. + +The second argument specifies the phase - :c:macro:`CPUFREQ_PRECHANGE` or +:c:macro:`CPUFREQ_POSTCHANGE`. + +The third argument is a :c:type:`struct cpufreq_freqs` with the following +values: + +| cpu - number of the affected CPU +| old - old frequency +| new - new frequency +| flags - flags of the cpufreq driver + + +3. CPUFreq Table Generation with Operating Performance Point (OPP) +------------------------------------------------------------------ +For details about OPP, see :file:`Documentation/power/opp.txt` + +:c:func:`dev_pm_opp_init_cpufreq_table` - This function provides a ready +to use conversion routine to translate the OPP layer's internal information +about the available frequencies into a format readily providable to cpufreq. + +WARNING: Do not use this function in interrupt context. + + Example:: + + soc_pm_init() + { + /* Do things */ + r = dev_pm_opp_init_cpufreq_table(dev, &freq_table); + if (!r) + policy->freq_table = freq_table; + /* Do other things */ + } + +NOTE: This function is available only if CONFIG_CPU_FREQ is enabled in +addition to CONFIG_PM_OPP. + +:c:func:`dev_pm_opp_free_cpufreq_table` - Free up the table allocated by :c:func:`dev_pm_opp_init_cpufreq_table` diff --git a/Documentation/cpu-freq/core.txt b/Documentation/cpu-freq/core.txt deleted file mode 100644 index 073f128af5a7..000000000000 --- a/Documentation/cpu-freq/core.txt +++ /dev/null @@ -1,120 +0,0 @@ - CPU frequency and voltage scaling code in the Linux(TM) kernel - - - L i n u x C P U F r e q - - C P U F r e q C o r e - - - Dominik Brodowski <linux@xxxxxxxx> - David Kimdon <dwhedon@xxxxxxxxxx> - Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> - Viresh Kumar <viresh.kumar@xxxxxxxxxx> - - - - Clock scaling allows you to change the clock speed of the CPUs on the - fly. This is a nice method to save battery power, because the lower - the clock speed, the less power the CPU consumes. - - -Contents: ---------- -1. CPUFreq core and interfaces -2. CPUFreq notifiers -3. CPUFreq Table Generation with Operating Performance Point (OPP) - -1. General Information -======================= - -The CPUFreq core code is located in drivers/cpufreq/cpufreq.c. This -cpufreq code offers a standardized interface for the CPUFreq -architecture drivers (those pieces of code that do actual -frequency transitions), as well as to "notifiers". These are device -drivers or other part of the kernel that need to be informed of -policy changes (ex. thermal modules like ACPI) or of all -frequency changes (ex. timing code) or even need to force certain -speed limits (like LCD drivers on ARM architecture). Additionally, the -kernel "constant" loops_per_jiffy is updated on frequency changes -here. - -Reference counting of the cpufreq policies is done by cpufreq_cpu_get -and cpufreq_cpu_put, which make sure that the cpufreq driver is -correctly registered with the core, and will not be unloaded until -cpufreq_put_cpu is called. That also ensures that the respective cpufreq -policy doesn't get freed while being used. - -2. CPUFreq notifiers -==================== - -CPUFreq notifiers conform to the standard kernel notifier interface. -See linux/include/linux/notifier.h for details on notifiers. - -There are two different CPUFreq notifiers - policy notifiers and -transition notifiers. - - -2.1 CPUFreq policy notifiers ----------------------------- - -These are notified when a new policy is intended to be set. Each -CPUFreq policy notifier is called twice for a policy transition: - -1.) During CPUFREQ_ADJUST all CPUFreq notifiers may change the limit if - they see a need for this - may it be thermal considerations or - hardware limitations. - -2.) And during CPUFREQ_NOTIFY all notifiers are informed of the new policy - - if two hardware drivers failed to agree on a new policy before this - stage, the incompatible hardware shall be shut down, and the user - informed of this. - -The phase is specified in the second argument to the notifier. - -The third argument, a void *pointer, points to a struct cpufreq_policy -consisting of several values, including min, max (the lower and upper -frequencies (in kHz) of the new policy). - - -2.2 CPUFreq transition notifiers --------------------------------- - -These are notified twice for each online CPU in the policy, when the -CPUfreq driver switches the CPU core frequency and this change has no -any external implications. - -The second argument specifies the phase - CPUFREQ_PRECHANGE or -CPUFREQ_POSTCHANGE. - -The third argument is a struct cpufreq_freqs with the following -values: -cpu - number of the affected CPU -old - old frequency -new - new frequency -flags - flags of the cpufreq driver - -3. CPUFreq Table Generation with Operating Performance Point (OPP) -================================================================== -For details about OPP, see Documentation/power/opp.txt - -dev_pm_opp_init_cpufreq_table - - This function provides a ready to use conversion routine to translate - the OPP layer's internal information about the available frequencies - into a format readily providable to cpufreq. - - WARNING: Do not use this function in interrupt context. - - Example: - soc_pm_init() - { - /* Do things */ - r = dev_pm_opp_init_cpufreq_table(dev, &freq_table); - if (!r) - policy->freq_table = freq_table; - /* Do other things */ - } - - NOTE: This function is available only if CONFIG_CPU_FREQ is enabled in - addition to CONFIG_PM_OPP. - -dev_pm_opp_free_cpufreq_table - Free up the table allocated by dev_pm_opp_init_cpufreq_table diff --git a/Documentation/cpu-freq/index.rst b/Documentation/cpu-freq/index.rst new file mode 100644 index 000000000000..fd81d4f501cc --- /dev/null +++ b/Documentation/cpu-freq/index.rst @@ -0,0 +1,14 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=============================================== +CPU Frequency and Voltage Scaling Documentation +=============================================== + +.. class:: toc-title + + Table of contents + +.. toctree:: + :maxdepth: 2 + + core.rst diff --git a/Documentation/index.rst b/Documentation/index.rst index a7566ef62411..934206bc1daf 100644 --- a/Documentation/index.rst +++ b/Documentation/index.rst @@ -102,6 +102,7 @@ needed). vm/index bpf/index misc-devices/index + cpu-freq/index Architecture-specific documentation ----------------------------------- -- 2.17.1