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* pm-cpufreq: (28 commits)
  MAINTAINERS: cpufreq: add bmips-cpufreq.c
  cpufreq: CPPC: add ACPI_PROCESSOR dependency
  cpufreq: make ti-cpufreq explicitly non-modular
  cpufreq: Do not clear real_cpus mask on policy init
  cpufreq: dt: Don't use generic platdev driver for ti-cpufreq platforms
  cpufreq: ti: Add cpufreq driver to determine available OPPs at runtime
  Documentation: dt: add bindings for ti-cpufreq
  cpufreq: qoriq: Don't look at clock implementation details
  cpufreq: qoriq: add ARM64 SoCs support
  cpufreq: brcmstb-avs-cpufreq: remove unnecessary platform_set_drvdata()
  cpufreq: s3c2416: double free on driver init error path
  MIPS: BMIPS: enable CPUfreq
  cpufreq: bmips-cpufreq: CPUfreq driver for Broadcom's BMIPS SoCs
  BMIPS: Enable prerequisites for CPUfreq in MIPS Kconfig.
  MIPS: BMIPS: Update defconfig
  cpufreq: Fix typos in comments
  cpufreq: intel_pstate: Calculate guaranteed performance for HWP
  cpufreq: intel_pstate: Make HWP limits compatible with legacy
  cpufreq: intel_pstate: Lower frequency than expected under no_turbo
  cpufreq: intel_pstate: Operation mode control from sysfs
  ...
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Rafael J. Wysocki committed Feb 20, 2017
2 parents 64f758a + 20bb550 commit f6cbe34
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24 changes: 13 additions & 11 deletions Documentation/cpu-freq/core.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,8 @@

Dominik Brodowski <linux@brodo.de>
David Kimdon <dwhedon@debian.org>
Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Viresh Kumar <viresh.kumar@linaro.org>



Expand Down Expand Up @@ -36,10 +38,11 @@ speed limits (like LCD drivers on ARM architecture). Additionally, the
kernel "constant" loops_per_jiffy is updated on frequency changes
here.

Reference counting is done by cpufreq_get_cpu and cpufreq_put_cpu,
which make sure that the cpufreq processor driver is correctly
registered with the core, and will not be unloaded until
cpufreq_put_cpu is called.
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
====================
Expand Down Expand Up @@ -69,18 +72,16 @@ CPUFreq policy notifier is called twice for a policy transition:
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 five values: cpu, min, max, policy and max_cpu_freq. min
and max are the lower and upper frequencies (in kHz) of the new
policy, policy the new policy, cpu the number of the affected CPU; and
max_cpu_freq the maximum supported CPU frequency. This value is given
for informational purposes only.
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 when the CPUfreq driver switches the CPU core
frequency and this change has any external implications.
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.
Expand All @@ -90,6 +91,7 @@ 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)
==================================================================
Expand Down
177 changes: 99 additions & 78 deletions Documentation/cpu-freq/cpu-drivers.txt
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Expand Up @@ -9,6 +9,8 @@


Dominik Brodowski <linux@brodo.de>
Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Viresh Kumar <viresh.kumar@linaro.org>



Expand Down Expand Up @@ -49,49 +51,65 @@ using cpufreq_register_driver()

What shall this struct cpufreq_driver contain?

cpufreq_driver.name - The name of this driver.
.name - The name of this driver.

cpufreq_driver.init - A pointer to the per-CPU initialization
function.
.init - A pointer to the per-policy initialization function.

cpufreq_driver.verify - A pointer to a "verification" function.
.verify - A pointer to a "verification" function.

cpufreq_driver.setpolicy _or_
cpufreq_driver.target/
target_index - See below on the differences.
.setpolicy _or_ .fast_switch _or_ .target _or_ .target_index - See
below on the differences.

And optionally

cpufreq_driver.exit - A pointer to a per-CPU cleanup
function called during CPU_POST_DEAD
phase of cpu hotplug process.
.flags - Hints for the cpufreq core.

cpufreq_driver.stop_cpu - A pointer to a per-CPU stop function
called during CPU_DOWN_PREPARE phase of
cpu hotplug process.
.driver_data - cpufreq driver specific data.

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/target_index or ->setpolicy.
.resolve_freq - Returns the most appropriate frequency for a target
frequency. Doesn't change the frequency though.

cpufreq_driver.attr - A pointer to a NULL-terminated list of
"struct freq_attr" which allow to
export values to sysfs.
.get_intermediate and target_intermediate - Used to switch to stable
frequency while changing CPU frequency.

cpufreq_driver.get_intermediate
and target_intermediate Used to switch to stable frequency while
changing CPU frequency.
.get - Returns current frequency of the CPU.

.bios_limit - Returns HW/BIOS max frequency limitations for the CPU.

.exit - A pointer to a per-policy cleanup function called during
CPU_POST_DEAD phase of cpu hotplug process.

.stop_cpu - A pointer to a per-policy stop function called during
CPU_DOWN_PREPARE phase of cpu hotplug process.

.suspend - A pointer to a per-policy suspend function which is called
with interrupts disabled and _after_ the governor is stopped for the
policy.

.resume - A pointer to a per-policy resume function which is called
with interrupts disabled and _before_ the governor is started again.

.ready - A pointer to a per-policy ready function which is called after
the policy is fully initialized.

.attr - A pointer to a NULL-terminated list of "struct freq_attr" which
allow to export values to sysfs.

.boost_enabled - If set, boost frequencies are enabled.

.set_boost - A pointer to a per-policy function to enable/disable boost
frequencies.


1.2 Per-CPU Initialization
--------------------------

Whenever a new CPU is registered with the device model, or after the
cpufreq driver registers itself, the per-CPU initialization function
cpufreq_driver.init is called. It takes a struct cpufreq_policy
*policy as argument. What to do now?
cpufreq driver registers itself, the per-policy initialization function
cpufreq_driver.init is called if no cpufreq policy existed for the CPU.
Note that the .init() and .exit() routines are called only once for the
policy and not for each CPU managed by the policy. It takes a struct
cpufreq_policy *policy as argument. What to do now?

If necessary, activate the CPUfreq support on your CPU.

Expand All @@ -117,47 +135,45 @@ policy->governor must contain the "default policy" for
cpufreq_driver.setpolicy or
cpufreq_driver.target/target_index is called
with these values.
policy->cpus Update this with the masks of the
(online + offline) CPUs that do DVFS
along with this CPU (i.e. that share
clock/voltage rails with it).

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
on them.

SMP systems normally have same clock source for a group of cpus. For these the
.init() would be called only once for the first online cpu. Here the .init()
routine must initialize policy->cpus with mask of all possible cpus (Online +
Offline) that share the clock. Then the core would copy this mask onto
policy->related_cpus and will reset policy->cpus to carry only online cpus.


1.3 verify
------------
----------

When the user decides a new policy (consisting of
"policy,governor,min,max") shall be set, this policy must be validated
so that incompatible values can be corrected. For verifying these
values, a frequency table helper and/or the
cpufreq_verify_within_limits(struct cpufreq_policy *policy, unsigned
int min_freq, unsigned int max_freq) function might be helpful. See
section 2 for details on frequency table helpers.
values cpufreq_verify_within_limits(struct cpufreq_policy *policy,
unsigned int min_freq, unsigned int max_freq) function might be helpful.
See section 2 for details on frequency table helpers.

You need to make sure that at least one valid frequency (or operating
range) is within policy->min and policy->max. If necessary, increase
policy->max first, and only if this is no solution, decrease policy->min.


1.4 target/target_index or setpolicy?
----------------------------
1.4 target or target_index or setpolicy or fast_switch?
-------------------------------------------------------

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/target_index call.
only allow the CPU frequency to be set to predefined fixed values. For
these, you use the ->target(), ->target_index() or ->fast_switch()
callbacks.

Some cpufreq-capable processors switch the frequency between certain
limits on their own. These shall use the ->setpolicy call
Some cpufreq capable processors switch the frequency between certain
limits on their own. These shall use the ->setpolicy() callback.


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).
Expand Down Expand Up @@ -186,9 +202,20 @@ actual frequency must be determined using the following rules:
Here again the frequency table helper might assist you - see section 2
for details.

1.6. fast_switch
----------------

1.6 setpolicy
---------------
This function is used for frequency switching from scheduler's context.
Not all drivers are expected to implement it, as sleeping from within
this callback isn't allowed. This callback must be highly optimized to
do switching as fast as possible.

This function has two arguments: struct cpufreq_policy *policy and
unsigned int target_frequency.


1.7 setpolicy
-------------

The setpolicy call only takes a struct cpufreq_policy *policy as
argument. You need to set the lower limit of the in-processor or
Expand All @@ -198,7 +225,7 @@ setting when policy->policy is CPUFREQ_POLICY_PERFORMANCE, and a
powersaving-oriented setting when CPUFREQ_POLICY_POWERSAVE. Also check
the reference implementation in drivers/cpufreq/longrun.c

1.7 get_intermediate and target_intermediate
1.8 get_intermediate and target_intermediate
--------------------------------------------

Only for drivers with target_index() and CPUFREQ_ASYNC_NOTIFICATION unset.
Expand All @@ -222,42 +249,36 @@ failures as core would send notifications for that.

As most cpufreq processors only allow for being set to a few specific
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
"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
CPUFREQ_ENTRY_INVALID. The entries don't need to be in ascending
order.

By calling cpufreq_table_validate_and_show(struct cpufreq_policy *policy,
struct cpufreq_frequency_table *table);
the cpuinfo.min_freq and cpuinfo.max_freq values are detected, and
policy->min and policy->max are set to the same values. This is
helpful for the per-CPU initialization stage.

int cpufreq_frequency_table_verify(struct cpufreq_policy *policy,
struct cpufreq_frequency_table *table);
assures that at least one valid frequency is within policy->min and
policy->max, and all other criteria are met. This is helpful for the
->verify call.

int cpufreq_frequency_table_target(struct cpufreq_policy *policy,
unsigned int target_freq,
unsigned int relation);

is the corresponding frequency table helper for the ->target
stage. Just pass the values to this function, and this function
returns the number of the frequency table entry which contains
the frequency the CPU shall be set to.
some work of the processor driver. Such a "frequency table" consists of
an array of struct cpufreq_frequency_table entries, with driver specific
values in "driver_data", the corresponding frequency in "frequency" and
flags set. 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
CPUFREQ_ENTRY_INVALID. The entries don't need to be in sorted in any
particular order, but if they are cpufreq core will do DVFS a bit
quickly for them as search for best match is faster.

By calling cpufreq_table_validate_and_show(), the cpuinfo.min_freq and
cpuinfo.max_freq values are detected, and policy->min and policy->max
are set to the same values. This is helpful for the per-CPU
initialization stage.

cpufreq_frequency_table_verify() assures that at least one valid
frequency is within policy->min and policy->max, and all other criteria
are met. This is helpful for the ->verify call.

cpufreq_frequency_table_target() is the corresponding frequency table
helper for the ->target stage. Just pass the values to this function,
and this function returns the of the frequency table entry which
contains 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,
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.
Expand Down
24 changes: 6 additions & 18 deletions Documentation/cpu-freq/cpufreq-stats.txt
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Expand Up @@ -34,10 +34,10 @@ cpufreq stats provides following statistics (explained in detail below).
- total_trans
- trans_table

All the statistics will be from the time the stats driver has been inserted
to the time when a read of a particular statistic is done. Obviously, stats
driver will not have any information about the frequency transitions before
the stats driver insertion.
All the statistics will be from the time the stats driver has been inserted
(or the time the stats were reset) to the time when a read of a particular
statistic is done. Obviously, stats driver will not have any information
about the frequency transitions before the stats driver insertion.

--------------------------------------------------------------------------------
<mysystem>:/sys/devices/system/cpu/cpu0/cpufreq/stats # ls -l
Expand Down Expand Up @@ -110,25 +110,13 @@ Config Main Menu
CPU Frequency scaling --->
[*] CPU Frequency scaling
[*] CPU frequency translation statistics
[*] CPU frequency translation statistics details


"CPU Frequency scaling" (CONFIG_CPU_FREQ) should be enabled to configure
cpufreq-stats.

"CPU frequency translation statistics" (CONFIG_CPU_FREQ_STAT) provides the
basic statistics which includes time_in_state and total_trans.
statistics which includes time_in_state, total_trans and trans_table.

"CPU frequency translation statistics details" (CONFIG_CPU_FREQ_STAT_DETAILS)
provides fine grained cpufreq stats by trans_table. The reason for having a
separate config option for trans_table is:
- trans_table goes against the traditional /sysfs rule of one value per
interface. It provides a whole bunch of value in a 2 dimensional matrix
form.

Once these two options are enabled and your CPU supports cpufrequency, you
Once this option is enabled and your CPU supports cpufrequency, you
will be able to see the CPU frequency statistics in /sysfs.




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