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linux-next/Documentation/ABI/testing/sysfs-class-devfreq
Rafael J. Wysocki d3569c149d Update devfreq for 5.11 
Detailed description for this pull request:
 
 1. Update devfreq core
 - Add new devfreq_frequency tracepoint to show the frequency change
 information.
 
 - Add governor feature flag. The devfreq governor is able to
 have the specific flag in order to contain the non-common feature.
 For example, if governor contains the 'immutable' feature, don't allow
 user to change the governor via sysfs.
 
 - Add governor sysfs attribute flag for each sysfs file. Prior to that
 devfreq subsystem show the all sysfs files regardless of governor type.
 But, some sysfs fils are not supported on the specific devfreq governor.
 In order to show the only supported sysfs files according to the governor,
 clarify the access permission of sysfs attributes according to governor.
 When adding the devfreq governor, can specify the available attribute
 information by using DEVFREQ_GOV_ATTR_* constant variable. The user can
 read or write the sysfs attributes in accordance to the specified attributes.
 
 - Clean-up the code to remove the duplicate code for the devfreq tracepoint
 and to remove redundant governor_name field from struct devfreq
 
 2. Update exynos-bus.c devfreq driver
 - Add interconnect API support for the Samsung Exynos Bus Frequency driver
 of exynos-bus.c. Complementing the devfreq driver with an interconnect
 functionality allows to ensure the QoS requirements of devices accessing
 the system memory (e.g. video processing devices) are fulfilled
 and allows to avoid issues like the DMA underrun.
 
 3. Update tegra devfreq driver
 - Add interconnect support and OPP interface for tegra30-devfreq.c.
 Also, it is to guarantee the QoS requirement of some devices like
 display controller.
 
 - Move tegra20-devfreq.c from drivers/devfreq/ into driver/memory/tegra/
 in order to use the more proper monitoring feature such as EMC_STAT
 which is based in driver/memory/tegra/.
 
 - Separate the configuration information for different SoC on
 tegra30-devfrqe.c. The tegra30-devfreq.c had been supported both
 tegra30-actmon and tegra124-actmon devices. In order to use
 the more correct configuration data, separate them.
 
 - Use dev_err_probe() to handle the deferred probe error on tegra30-devfreq.c.
 
 4. Pull the request of 'Tegra SoC and clock controller changes for v5.11'
 sent by Krzysztof Kozlowski <krzk@kernel.org> in order to prevent the
 build error.
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Merge tag 'devfreq-next-for-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/chanwoo/linux

Pull devfreq updates for 5.11 from Chanwoo Choi:

 1. Update devfreq core

  - Add new devfreq_frequency tracepoint to show the frequency change
    information.

  - Add governor feature flag. The devfreq governor is able to set the
    specific flag in order to support a non-common feature. For
    example, if the governor supports the 'immutable' feature, don't
    allow user space to change the governor via sysfs.

  - Add governor sysfs attribute flag for each sysfs file. Prior to that
    the devfreq subsystem allowed all of the sysfs files to be accessed
    regardless of the governor type. But some sysfs fils are not
    supported by specific devfreq governors. In order to only allow the
    sysfs files supported by the governor to be accessed, clarify the
    access permissions of sysfs attributes according to the governor.
    When adding the devfreq governor, specify the available attribute
    information by using DEVFREQ_GOV_ATTR_* symbols. The user can read
    or write the sysfs attributes in accordance to the specified
    access permissions.

  - Clean-up the code to reduce duplication for the devfreq tracepoint
    and to remove redundant governor_name field from struct devfreq.

 2. Update exynos-bus.c devfreq driver

  - Add interconnect API support to the Samsung Exynos Bus Frequency
    driver, exynos-bus.c. Complementing the devfreq driver with
    interconnect functionality allows to ensure that the QoS
    requirements regarding devices accessing the system memory (e.g.
    video processing devices) will be met and allows to avoid issues
    like DMA underrun.

 3. Update tegra devfreq driver

  - Add interconnect support and OPP interface to tegra30-devfreq.c.
    Also, it is to guarantee the QoS requirement of some devices like
    the display controller.

  - Move tegra20-devfreq.c from drivers/devfreq/ into drivers/memory/tegra/
    in order to use the more proper monitoring feature such as EMC_STAT
    which is located in drivers/memory/tegra/.

  - Separate the configuration information for different SoCs in
    tegra30-devfrqe.c. The tegra30-devfreq.c had been supporting both
    tegra30-actmon and tegra124-actmon devices. In order to use the
    more correct configuration data, separate them.

  - Use dev_err_probe() to handle the deferred probe error in
    tegra30-devfreq.c.

 4. Pull the request of 'Tegra SoC and clock controller changes for
    v5.11' sent by Krzysztof Kozlowski <krzk@kernel.org> in order to
    avoid a build error."

* tag 'devfreq-next-for-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/chanwoo/linux:
  PM / devfreq: tegra30: Separate configurations per-SoC generation
  PM / devfreq: tegra30: Support interconnect and OPPs from device-tree
  PM / devfreq: tegra20: Deprecate in a favor of emc-stat based driver
  PM / devfreq: exynos-bus: Add registration of interconnect child device
  dt-bindings: devfreq: Add documentation for the interconnect properties
  soc/tegra: fuse: Add stub for tegra_sku_info
  soc/tegra: fuse: Export tegra_read_ram_code()
  clk: tegra: Export Tegra20 EMC kernel symbols
  PM / devfreq: tegra30: Silence deferred probe error
  PM / devfreq: tegra20: Relax Kconfig dependency
  PM / devfreq: tegra20: Silence deferred probe error
  PM / devfreq: Remove redundant governor_name from struct devfreq
  PM / devfreq: Add governor attribute flag for specifc sysfs nodes
  PM / devfreq: Add governor feature flag
  PM / devfreq: Add tracepoint for frequency changes
  PM / devfreq: Unify frequency change to devfreq_update_target func
  trace: events: devfreq: Use fixed indentation size to improve readability
2020-12-11 19:40:00 +01:00

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What: /sys/class/devfreq/.../
Date: September 2011
Contact: MyungJoo Ham <myungjoo.ham@samsung.com>
Description:
Provide a place in sysfs for the devfreq objects.
This allows accessing various devfreq specific variables.
The name of devfreq object denoted as ... is same as the
name of device using devfreq.
What: /sys/class/devfreq/.../name
Date: November 2019
Contact: Chanwoo Choi <cw00.choi@samsung.com>
Description:
The /sys/class/devfreq/.../name shows the name of device
of the corresponding devfreq object.
What: /sys/class/devfreq/.../governor
Date: September 2011
Contact: MyungJoo Ham <myungjoo.ham@samsung.com>
Description:
The /sys/class/devfreq/.../governor show or set the name of the
governor used by the corresponding devfreq object.
What: /sys/class/devfreq/.../cur_freq
Date: September 2011
Contact: MyungJoo Ham <myungjoo.ham@samsung.com>
Description:
The /sys/class/devfreq/.../cur_freq shows the current
frequency of the corresponding devfreq object. Same as
target_freq when get_cur_freq() is not implemented by
devfreq driver.
What: /sys/class/devfreq/.../target_freq
Date: September 2012
Contact: Rajagopal Venkat <rajagopal.venkat@linaro.org>
Description:
The /sys/class/devfreq/.../target_freq shows the next governor
predicted target frequency of the corresponding devfreq object.
What: /sys/class/devfreq/.../trans_stat
Date: October 2012
Contact: MyungJoo Ham <myungjoo.ham@samsung.com>
Description:
This ABI shows or clears the statistics of devfreq behavior
on a specific device. It shows the time spent in each state
and the number of transitions between states.
In order to activate this ABI, the devfreq target device
driver should provide the list of available frequencies
with its profile. If need to reset the statistics of devfreq
behavior on a specific device, enter 0(zero) to 'trans_stat'
as following::
echo 0 > /sys/class/devfreq/.../trans_stat
What: /sys/class/devfreq/.../available_frequencies
Date: October 2012
Contact: Nishanth Menon <nm@ti.com>
Description:
The /sys/class/devfreq/.../available_frequencies shows
the available frequencies of the corresponding devfreq object.
This is a snapshot of available frequencies and not limited
by the min/max frequency restrictions.
What: /sys/class/devfreq/.../available_governors
Date: October 2012
Contact: Nishanth Menon <nm@ti.com>
Description:
The /sys/class/devfreq/.../available_governors shows
currently available governors in the system.
What: /sys/class/devfreq/.../min_freq
Date: January 2013
Contact: MyungJoo Ham <myungjoo.ham@samsung.com>
Description:
The /sys/class/devfreq/.../min_freq shows and stores
the minimum frequency requested by users. It is 0 if
the user does not care. min_freq overrides the
frequency requested by governors.
What: /sys/class/devfreq/.../max_freq
Date: January 2013
Contact: MyungJoo Ham <myungjoo.ham@samsung.com>
Description:
The /sys/class/devfreq/.../max_freq shows and stores
the maximum frequency requested by users. It is 0 if
the user does not care. max_freq overrides the
frequency requested by governors and min_freq.
The max_freq overrides min_freq because max_freq may be
used to throttle devices to avoid overheating.
What: /sys/class/devfreq/.../polling_interval
Date: September 2011
Contact: MyungJoo Ham <myungjoo.ham@samsung.com>
Description:
The /sys/class/devfreq/.../polling_interval shows and sets
the requested polling interval of the corresponding devfreq
object. The values are represented in ms. If the value is
less than 1 jiffy, it is considered to be 0, which means
no polling. This value is meaningless if the governor is
not polling; thus. If the governor is not using
devfreq-provided central polling
(/sys/class/devfreq/.../central_polling is 0), this value
may be useless.
A list of governors that support the node:
- simple_ondmenad
- tegra_actmon
What: /sys/class/devfreq/.../userspace/set_freq
Date: September 2011
Contact: MyungJoo Ham <myungjoo.ham@samsung.com>
Description:
The /sys/class/devfreq/.../userspace/set_freq shows and
sets the requested frequency for the devfreq object if
userspace governor is in effect.
A list of governors that support the node:
- userspace
What: /sys/class/devfreq/.../timer
Date: July 2020
Contact: Chanwoo Choi <cw00.choi@samsung.com>
Description:
This ABI shows and stores the kind of work timer by users.
This work timer is used by devfreq workqueue in order to
monitor the device status such as utilization. The user
can change the work timer on runtime according to their demand
as following::
echo deferrable > /sys/class/devfreq/.../timer
echo delayed > /sys/class/devfreq/.../timer
A list of governors that support the node:
- simple_ondemand
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