mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-16 17:23:55 +08:00
docs: cpu-freq: convert cpu-drivers.txt to ReST
- Add a SPDX header; - Add a document title, based on the original contents of cpu-freq/index.txt; - Use lists where needed; - Comment out the existing text-only index; - Adjust some title marks; - Add table markups; - Add notes markups; - Mark literal blocks as such; - use ``foo`` for literal texts; - Some whitespace fixes and new line breaks; - Add it to cpu-freq/index.rst. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Mauro Carvalho Chehab
Rafael J. Wysocki
parent
c460f972d3
commit
8f92058987
@ -1,35 +1,27 @@
|
||||
CPU frequency and voltage scaling code in the Linux(TM) kernel
|
||||
.. SPDX-License-Identifier: GPL-2.0
|
||||
|
||||
===============================================
|
||||
How to Implement a new CPUFreq Processor Driver
|
||||
===============================================
|
||||
|
||||
Authors:
|
||||
|
||||
|
||||
L i n u x C P U F r e q
|
||||
- Dominik Brodowski <linux@brodo.de>
|
||||
- Rafael J. Wysocki <rafael.j.wysocki@intel.com>
|
||||
- Viresh Kumar <viresh.kumar@linaro.org>
|
||||
|
||||
C P U D r i v e r s
|
||||
.. Contents
|
||||
|
||||
- information for developers -
|
||||
|
||||
|
||||
Dominik Brodowski <linux@brodo.de>
|
||||
Rafael J. Wysocki <rafael.j.wysocki@intel.com>
|
||||
Viresh Kumar <viresh.kumar@linaro.org>
|
||||
|
||||
|
||||
|
||||
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. What To Do?
|
||||
1.1 Initialization
|
||||
1.2 Per-CPU Initialization
|
||||
1.3 verify
|
||||
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
|
||||
1. What To Do?
|
||||
1.1 Initialization
|
||||
1.2 Per-CPU Initialization
|
||||
1.3 verify
|
||||
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
|
||||
|
||||
|
||||
|
||||
@ -49,7 +41,7 @@ function check whether this kernel runs on the right CPU and the right
|
||||
chipset. If so, register a struct cpufreq_driver with the CPUfreq core
|
||||
using cpufreq_register_driver()
|
||||
|
||||
What shall this struct cpufreq_driver contain?
|
||||
What shall this struct cpufreq_driver contain?
|
||||
|
||||
.name - The name of this driver.
|
||||
|
||||
@ -108,37 +100,42 @@ Whenever a new CPU is registered with the device model, or after the
|
||||
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?
|
||||
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.
|
||||
|
||||
Then, the driver must fill in the following values:
|
||||
|
||||
policy->cpuinfo.min_freq _and_
|
||||
policy->cpuinfo.max_freq - the minimum and maximum frequency
|
||||
(in kHz) which is supported by
|
||||
this CPU
|
||||
policy->cpuinfo.transition_latency the time it takes on this CPU to
|
||||
switch between two frequencies in
|
||||
nanoseconds (if appropriate, else
|
||||
specify CPUFREQ_ETERNAL)
|
||||
|
||||
policy->cur The current operating frequency of
|
||||
this CPU (if appropriate)
|
||||
policy->min,
|
||||
policy->max,
|
||||
policy->policy and, if necessary,
|
||||
policy->governor must contain the "default policy" for
|
||||
this CPU. A few moments later,
|
||||
cpufreq_driver.verify and either
|
||||
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).
|
||||
+-----------------------------------+--------------------------------------+
|
||||
|policy->cpuinfo.min_freq _and_ | |
|
||||
|policy->cpuinfo.max_freq | the minimum and maximum frequency |
|
||||
| | (in kHz) which is supported by |
|
||||
| | this CPU |
|
||||
+-----------------------------------+--------------------------------------+
|
||||
|policy->cpuinfo.transition_latency | the time it takes on this CPU to |
|
||||
| | switch between two frequencies in |
|
||||
| | nanoseconds (if appropriate, else |
|
||||
| | specify CPUFREQ_ETERNAL) |
|
||||
+-----------------------------------+--------------------------------------+
|
||||
|policy->cur | The current operating frequency of |
|
||||
| | this CPU (if appropriate) |
|
||||
+-----------------------------------+--------------------------------------+
|
||||
|policy->min, | |
|
||||
|policy->max, | |
|
||||
|policy->policy and, if necessary, | |
|
||||
|policy->governor | must contain the "default policy" for|
|
||||
| | this CPU. A few moments later, |
|
||||
| | cpufreq_driver.verify and either |
|
||||
| | 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
|
||||
@ -151,8 +148,8 @@ on them.
|
||||
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 cpufreq_verify_within_limits(struct cpufreq_policy *policy,
|
||||
unsigned int min_freq, unsigned int max_freq) function might be helpful.
|
||||
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
|
||||
@ -163,7 +160,7 @@ policy->max first, and only if this is no solution, decrease policy->min.
|
||||
1.4 target or target_index or setpolicy or fast_switch?
|
||||
-------------------------------------------------------
|
||||
|
||||
Most cpufreq drivers or even most cpu frequency scaling algorithms
|
||||
Most cpufreq drivers or even most cpu frequency scaling algorithms
|
||||
only allow the CPU frequency to be set to predefined fixed values. For
|
||||
these, you use the ->target(), ->target_index() or ->fast_switch()
|
||||
callbacks.
|
||||
@ -175,8 +172,8 @@ 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).
|
||||
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.
|
||||
@ -184,9 +181,9 @@ 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:
|
||||
Deprecated
|
||||
----------
|
||||
The target call has three arguments: struct cpufreq_policy *policy,
|
||||
The target call has three arguments: ``struct cpufreq_policy *policy``,
|
||||
unsigned int target_frequency, unsigned int relation.
|
||||
|
||||
The CPUfreq driver must set the new frequency when called here. The
|
||||
@ -210,14 +207,14 @@ 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.
|
||||
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
|
||||
The setpolicy call only takes a ``struct cpufreq_policy *policy`` as
|
||||
argument. You need to set the lower limit of the in-processor or
|
||||
in-chipset dynamic frequency switching to policy->min, the upper limit
|
||||
to policy->max, and -if supported- select a performance-oriented
|
||||
@ -278,10 +275,10 @@ 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.
|
||||
Use arguments "pos" - a ``cpufreq_frequency_table *`` as a loop cursor and
|
||||
"table" - the ``cpufreq_frequency_table *`` you want to iterate over.
|
||||
|
||||
For example:
|
||||
For example::
|
||||
|
||||
struct cpufreq_frequency_table *pos, *driver_freq_table;
|
||||
|
||||
@ -15,6 +15,7 @@ Author: Dominik Brodowski <linux@brodo.de>
|
||||
:maxdepth: 1
|
||||
|
||||
core
|
||||
cpu-drivers
|
||||
|
||||
Mailing List
|
||||
------------
|
||||
|
||||
Loading…
Reference in New Issue
Block a user