linux-kernel - [PATCH v3 0/2] PM / devfreq: Add governor feature and attribute flag

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Message-Id: <20201007050703.20759-1-cw00.choi@samsung.com>
Date:   Wed,  7 Oct 2020 14:07:01 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-tegra@...r.kernel.org
Cc:     digetx@...il.com, leonard.crestez@....com, lukasz.luba@....com,
        enric.balletbo@...labora.com, hl@...k-chips.com,
        thierry.reding@...il.com, jonathanh@...dia.com, abel.vesa@....com,
        k.konieczny@...sung.com, b.zolnierkie@...sung.com,
        cw00.choi@...sung.com, chanwoo@...nel.org,
        myungjoo.ham@...sung.com, kyungmin.park@...sung.com
Subject: [PATCH v3 0/2] PM / devfreq: Add governor feature and attribute
 flag

Each devfreq governor can have the different sysfs attributes and features.
In order to provide the only available sysfs attribute to user-space,
add governor attribute flag with DEVFREQ_GOV_ATTR_[attribute name] defintion.

Also, each governor is able to have the specific flag in order to
support specific feature with DEVFREQ_GOV_FLAG_[feature name] defintion
like immutable governor.

According to each governor, can initiate the governor feature and attribute
flags.

[Common sysfs attributes for devfreq class]
And all devfreq governors have to support the following common attributes.
The common attributes are added to devfreq class by default.
- governor
- available_governors
- available_frequencies
- cur_freq
- target_freq
- min_freq
- max_freq
- trans_stat

[Definition for governor attribute flag]
- DEVFREQ_GOV_ATTR_POLLING_INTERVAL to update polling interval for timer.
  : /sys/class/devfreq/[devfreq dev name]/polling_interval
- DEVFREQ_GOV_ATTR_TIMER to change the type of timer on either deferrable
  or dealyed timer.
  : /sys/class/devfreq/[devfreq dev name]/timer

[Definition for governor feature flag]
- DEVFREQ_GOV_FLAG_IMMUTABLE
  : If immutable flag is set, governor is never changeable to other governors.
- DEVFREQ_GOV_FLAG_IRQ_DRIVEN
  : Devfreq core won't schedule polling work for this governor if value is set.

[Table of governor attribute flags for evfreq governors]
-----------------------------------------------------------------------------
                      | simple    | perfor | power | user | passive | tegra30
		      | ondemand  | mance  | save  | space|         |
------------------------------------------------------------------------------
governor              | O         | O      | O     | O    | O       | O
available_governors   | O         | O      | O     | O    | O       | O
available_frequencies | O         | O      | O     | O    | O       | O
cur_freq              | O         | O      | O     | O    | O       | O
target_freq           | O         | O      | O     | O    | O       | O
min_freq              | O         | O      | O     | O    | O       | O
max_freq              | O         | O      | O     | O    | O       | O
trans_stat            | O         | O      | O     | O    | O       | O
------------------------------------------------------------------------------
polling_interval      | O         | X      | X     | X    | X       | O
timer                 | O         | X      | X     | X    | X       | X
------------------------------------------------------------------------------
immutable             | X         | X      | X     | X    | O       | O
interrupt_driven      | X(polling)| X      | X     | X    | X       | O (irq)
------------------------------------------------------------------------------

Changes from v2:
- https://lkml.org/lkml/2020/7/13/285 ("[PATCH v2 0/2] PM / devfreq: Add governor flags")
- Hide unsupported sysfs node to user-space instead of checking the permission
of sysfs node.

Chanwoo Choi (2):
  PM / devfreq: Add governor feature flag
  PM / devfreq: Add governor attribute flag for specifc sysfs nodes

 Documentation/ABI/testing/sysfs-class-devfreq |  54 +++---
 drivers/devfreq/devfreq.c                     | 170 +++++++++++-------
 drivers/devfreq/governor.h                    |  30 +++-
 drivers/devfreq/governor_passive.c            |   2 +-
 drivers/devfreq/governor_simpleondemand.c     |   2 +
 drivers/devfreq/tegra30-devfreq.c             |   5 +-
 6 files changed, 171 insertions(+), 92 deletions(-)

-- 
2.17.1