Commit Graph

282 Commits

Author SHA1 Message Date
Nishanth Menon 3aa173b8db PM / devfreq: provide hooks for governors to be registered
Add devfreq_add_governor and devfreq_remove_governor which
can be invoked by governors to register with devfreq.

This sets up the stage to dynamically switch governors and
allow governors to be dynamically loaded as well.

Cc: Rajagopal Venkat <rajagopal.venkat@linaro.org>
Cc: MyungJoo Ham <myungjoo.ham@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Kevin Hilman <khilman@ti.com>
Cc: linux-pm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

Signed-off-by: Nishanth Menon <nm@ti.com>
Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com>
2012-11-20 18:46:12 +09:00
Nishanth Menon 2df5021fa9 PM / devfreq: export update_devfreq
Allow update_devfreq to be used by devfreq governor built
as modules

Cc: Rajagopal Venkat <rajagopal.venkat@linaro.org>
Cc: MyungJoo Ham <myungjoo.ham@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Kevin Hilman <khilman@ti.com>
Cc: linux-pm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

Signed-off-by: Nishanth Menon <nm@ti.com>
Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
2012-11-20 16:06:03 +09:00
Jonghwa Lee e552bbaf5b PM / devfreq: Add sysfs node for representing frequency transition information.
This patch adds sysfs node which can be used to get information of frequency
transition. It represents transition table which contains total number of transition of
each freqeuncy state and time spent. It is inspired CPUFREQ's status driver.

Signed-off-by: Jonghwa Lee <jonghwa3.lee@samsung.com>
[Added Documentation/ABI entry, updated kernel-doc, and resolved merge conflict]
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
2012-11-20 16:05:44 +09:00
Nishanth Menon d287de855f PM / devfreq: Add sysfs node to expose available frequencies
devfreq governors such as ondemand are controlled by a min and
max frequency, while governors like userspace governor allow us
to set a specific frequency.
However, for the same specific device, depending on the SoC, the
available frequencies can vary.

So expose the available frequencies as a snapshot over sysfs to
allow informed decisions.

This was inspired by cpufreq framework's equivalent for similar
usage sysfs node: scaling_available_frequencies.

Cc: Rajagopal Venkat <rajagopal.venkat@linaro.org>
Cc: MyungJoo Ham <myungjoo.ham@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Kevin Hilman <khilman@ti.com>
Cc: linux-pm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
2012-11-20 15:59:32 +09:00
Sachin Kamat d7895052d9 PM / devfreq: Use devm_* functions in exynos4_bus.c
devm_* functions are device managed functions and make cleanup code
simpler and smaller.
devm_kzalloc and devm_regulator_get functions are used.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
[renamed the patch title by MyungJoo Ham]
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
2012-11-20 15:59:22 +09:00
Nishanth Menon 0779726cc2 PM / OPP: predictable fail results for opp_find* functions, v2
Currently the opp_find* functions return -ENODEV when:
a) it cant find a device (e.g. request for an OPP search on device
   which was not registered)
b) When it cant find a match for the search strategy used

This makes life a little in-efficient for users such as devfreq
to make reasonable judgement before switching search strategies.

So, standardize the return results as following:
 -EINVAL for bad pointer parameters
 -ENODEV when device cannot be found
 -ERANGE when search fails

This has the following benefit for devfreq implementation:
The search fails when an unregistered device pointer is provided.
This is a trigger to change the search direction and search for
a better fit, however, if we cannot differentiate between a valid
search range failure Vs an unregistered device, second search goes
through the same fail return condition. This can be avoided by
appropriate handling of error return code.

With this change, we also fix devfreq for the improved search
strategy with updated error code.

Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Kevin Hilman <khilman@ti.com>
Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2012-11-15 00:36:10 +01:00
Nishanth Menon 1a1357ea17 PM / devfreq: make devfreq_class static
devfreq_class is used internally by devfreq and has no
need to be globally available.

This also fixes the following sparse warning:
drivers/devfreq/devfreq.c:30:14: warning: symbol 'devfreq_class' was not declared. Should it be static?

Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2012-11-15 00:35:06 +01:00
Nishanth Menon 12e26265e6 PM / devfreq: fix sscanf handling for writable sysfs entries
sscanf returns 0 when an invalid parameter like:
echo -n "a">min_freq
is attempted. Returning back the return result(0) will
cause the command not to return back to command
prompt.

Instead, just return -EINVAL when sscanf does not
return 1.

This is done for min_freq, max_freq and polling_interval

Signed-off-by: Nishanth Menon <nm@ti.com>
Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2012-11-15 00:35:05 +01:00
Nishanth Menon c5b4a1c15d PM / devfreq: kernel-doc typo corrections
Parameter documentation needs a ':' for scripts/kernel-doc
to parse properly.

Minor fixes for ones warned by:
./scripts/kernel-doc -text drivers/devfreq/devfreq.c>/dev/null

Signed-off-by: Nishanth Menon <nm@ti.com>
Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2012-11-15 00:35:05 +01:00
Rajagopal Venkat 7f98a905dc PM / devfreq: Add current freq callback in device profile
Devfreq returns governor predicted frequency as current frequency
via sysfs interface. But device may not support all frequencies
that governor predicts. So add a callback in device profile to get
current freq from driver. Also add a new sysfs node to expose
governor predicted next target frequency.

Signed-off-by: Rajagopal Venkat <rajagopal.venkat@linaro.org>
Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2012-11-15 00:35:04 +01:00
Rajagopal Venkat 206c30cfeb PM / devfreq: Add suspend and resume apis
Add devfreq suspend/resume apis for devfreq users. This patch
supports suspend and resume of devfreq load monitoring, required
for devices which can idle.

Signed-off-by: Rajagopal Venkat <rajagopal.venkat@linaro.org>
Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2012-11-15 00:35:04 +01:00
Rajagopal Venkat 7e6fdd4bad PM / devfreq: Core updates to support devices which can idle
Prepare devfreq core framework to support devices which
can idle. When device idleness is detected perhaps through
runtime-pm, need some mechanism to suspend devfreq load
monitoring and resume back when device is online. Present
code continues monitoring unless device is removed from
devfreq core.

This patch introduces following design changes,

 - use per device work instead of global work to monitor device
   load. This enables suspend/resume of device devfreq and
   reduces monitoring code complexity.
 - decouple delayed work based load monitoring logic from core
   by introducing helpers functions to be used by governors. This
   provides flexibility for governors either to use delayed work
   based monitoring functions or to implement their own mechanism.
 - devfreq core interacts with governors via events to perform
   specific actions. These events include start/stop devfreq.
   This sets ground for adding suspend/resume events.

The devfreq apis are not modified and are kept intact.

Signed-off-by: Rajagopal Venkat <rajagopal.venkat@linaro.org>
Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2012-11-15 00:35:04 +01:00
Tejun Heo 203b42f731 workqueue: make deferrable delayed_work initializer names consistent
Initalizers for deferrable delayed_work are confused.

* __DEFERRED_WORK_INITIALIZER()
* DECLARE_DEFERRED_WORK()
* INIT_DELAYED_WORK_DEFERRABLE()

Rename them to

* __DEFERRABLE_WORK_INITIALIZER()
* DECLARE_DEFERRABLE_WORK()
* INIT_DEFERRABLE_WORK()

This patch doesn't cause any functional changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
2012-08-21 13:18:23 -07:00
Linus Torvalds 468f4d1a85 Power management updates for 3.5
* Implementation of opportunistic suspend (autosleep) and user space interface
   for manipulating wakeup sources.
 
 * Hibernate updates from Bojan Smojver and Minho Ban.
 
 * Updates of the runtime PM core and generic PM domains framework related to
   PM QoS.
 
 * Assorted fixes.
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Merge tag 'pm-for-3.5' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

Pull power management updates from Rafael Wysocki:

 - Implementation of opportunistic suspend (autosleep) and user space
   interface for manipulating wakeup sources.

 - Hibernate updates from Bojan Smojver and Minho Ban.

 - Updates of the runtime PM core and generic PM domains framework
   related to PM QoS.

 - Assorted fixes.

* tag 'pm-for-3.5' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: (25 commits)
  epoll: Fix user space breakage related to EPOLLWAKEUP
  PM / Domains: Make it possible to add devices to inactive domains
  PM / Hibernate: Use get_gendisk to verify partition if resume_file is integer format
  PM / Domains: Fix computation of maximum domain off time
  PM / Domains: Fix link checking when add subdomain
  PM / Sleep: User space wakeup sources garbage collector Kconfig option
  PM / Sleep: Make the limit of user space wakeup sources configurable
  PM / Documentation: suspend-and-cpuhotplug.txt: Fix typo
  PM / Domains: Cache device stop and domain power off governor results, v3
  PM / Domains: Make device removal more straightforward
  PM / Sleep: Fix a mistake in a conditional in autosleep_store()
  epoll: Add a flag, EPOLLWAKEUP, to prevent suspend while epoll events are ready
  PM / QoS: Create device constraints objects on notifier registration
  PM / Runtime: Remove device fields related to suspend time, v2
  PM / Domains: Rework default domain power off governor function, v2
  PM / Domains: Rework default device stop governor function, v2
  PM / Sleep: Add user space interface for manipulating wakeup sources, v3
  PM / Sleep: Add "prevent autosleep time" statistics to wakeup sources
  PM / Sleep: Implement opportunistic sleep, v2
  PM / Sleep: Add wakeup_source_activate and wakeup_source_deactivate tracepoints
  ...
2012-05-23 14:07:06 -07:00
Xiaoguang Chen 0b7c328fd3 PM: devfreq: init performance/powersave governor
Performance and powersave governor's get_target_freq
is not called if driver chooses one of these two governors.
Add init function in governor profile to call update_devfreq
which will call get_target_freq subsequently.

Signed-off-by: Xiaoguang Chen <chenxg@marvell.com>
Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
2012-05-01 21:23:50 +02:00
Masanari Iida 6b2aac42b2 Fix typo in various Kconfig file
Correct spelling typo in various Kconfig file.

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2012-04-16 14:40:08 +02:00
Linus Torvalds d61b7a572b ARM: global cleanups
Quite a bit of code gets removed, and some stuff moved around, mostly
 the old samsung s3c24xx stuff. There should be no functional changes
 in this series otherwise. Some cleanups have dependencies on other
 arm-soc branches and will be sent in the second round.
 
 Signed-off-by: Arnd Bergmann <arnd@arndb.de>
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Merge tag 'cleanup' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc

Pull "ARM: global cleanups" from Arnd Bergmann:
 "Quite a bit of code gets removed, and some stuff moved around, mostly
  the old samsung s3c24xx stuff.  There should be no functional changes
  in this series otherwise.  Some cleanups have dependencies on other
  arm-soc branches and will be sent in the second round.

  Signed-off-by: Arnd Bergmann <arnd@arndb.de>"

Fixed up trivial conflicts mainly due to #include's being changes on
both sides.

* tag 'cleanup' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc: (121 commits)
  ep93xx: Remove unnecessary includes of ep93xx-regs.h
  ep93xx: Move EP93XX_SYSCON defines to SoC private header
  ep93xx: Move crunch code to mach-ep93xx directory
  ep93xx: Make syscon access functions private to SoC
  ep93xx: Configure GPIO ports in core code
  ep93xx: Move peripheral defines to local SoC header
  ep93xx: Convert the watchdog driver into a platform device.
  ep93xx: Use ioremap for backlight driver
  ep93xx: Move GPIO defines to gpio-ep93xx.h
  ep93xx: Don't use system controller defines in audio drivers
  ep93xx: Move PHYS_BASE defines to local SoC header file
  ARM: EXYNOS: Add clock register addresses for EXYNOS4X12 bus devfreq driver
  ARM: EXYNOS: add clock registers for exynos4x12-cpufreq
  PM / devfreq: update the name of EXYNOS clock registers that were omitted
  PM / devfreq: update the name of EXYNOS clock register
  ARM: EXYNOS: change the prefix S5P_ to EXYNOS4_ for clock
  ARM: EXYNOS: use static declaration on regarding clock
  ARM: EXYNOS: replace clock.c for other new EXYNOS SoCs
  ARM: OMAP2+: Fix build error after merge
  ARM: S3C24XX: remove call to s3c24xx_setup_clocks
  ...
2012-03-27 16:03:32 -07:00
MyungJoo Ham ab5f299f51 PM / devfreq: add relation of recommended frequency.
The semantics of "target frequency" given to devfreq driver from
devfreq framework has always been interpretted as "at least" or GLB
(greatest lower bound). However, the framework might want the
device driver to limit its max frequency (LUB: least upper bound),
especially if it is given by thermal framework (it's too hot).

Thus, the target fuction should have another parameter to express
whether the framework wants GLB or LUB. And, the additional parameter,
"u32 flags", does it.

With the update, devfreq_recommended_opp() is also updated.

Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Mike Turquette <mturquette@ti.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
2012-03-17 21:51:34 +01:00
MyungJoo Ham a2b9676db0 PM / devfreq: update the name of EXYNOS clock registers that were omitted
In the commit, "PM / devfreq: update the name of EXYNOS clock register"
ommitted one register.

Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>
2012-03-10 22:30:21 -08:00
Kukjin Kim 5fcc9297b8 PM / devfreq: update the name of EXYNOS clock register
According to replacing the name of EXYNOS clock registers,
this patch updates exynos4_bus.c file where it is used.

Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>
2012-03-10 22:30:16 -08:00
MyungJoo Ham 6530b9dea1 PM / devfreq: add min/max_freq limit requested by users.
The frequency requested to devfreq device driver from devfreq governors
is restricted by min_freq and max_freq input.

Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
2012-01-20 10:12:38 +09:00
Axel Lin e0d44e8ab0 devfreq: Remove MODULE_ALIAS for exynos4 busfreq driver
This driver can only be built-in, it does not make sense to add modalias for
it (in addition to being incorrect, the platform modalias needs to be prefixed
with "platform:").

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
2012-01-20 10:12:38 +09:00
Axel Lin f0c28b0075 devfreq: exynos4_bus: Use dev_get_drvdata at appropriate places
Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
2012-01-20 10:12:37 +09:00
Rafael J. Wysocki dfa9d178cd Merge branch 'devfreq-for-next' of git://git.infradead.org/users/kmpark/linux-samsung into pm-devfreq
* 'devfreq-for-next' of git://git.infradead.org/users/kmpark/linux-samsung: (765 commits)
  PM/Devfreq: Add Exynos4-bus device DVFS driver for Exynos4210/4212/4412.
  pci: Fix hotplug of Express Module with pci bridges
  i2c-eg20t: correct the driver init order of pch_i2c_probe()
  I2C: OMAP: fix FIFO usage for OMAP4
  i2c-s3c2410: Fix return code of s3c24xx_i2c_parse_dt_gpio
  i2c: i2c-s3c2410: Add a cpu_relax() to busy wait for bus idle
  Linux 3.2-rc6
  Revert "drm/i915: fix infinite recursion on unbind due to ilk vt-d w/a"
  btrfs: lower the dirty balance poll interval
  drm/i915/dp: Dither down to 6bpc if it makes the mode fit
  drm/i915: enable semaphores on per-device defaults
  drm/i915: don't set unpin_work if vblank_get fails
  drm/i915: By default, enable RC6 on IVB and SNB when reasonable
  iommu: Export intel_iommu_enabled to signal when iommu is in use
  drm/i915/sdvo: Include LVDS panels for the IS_DIGITAL check
  drm/i915: prevent division by zero when asking for chipset power
  drm/i915: add PCH info to i915_capabilities
  drm/i915: set the right SDVO transcoder for CPT
  drm/i915: no-lvds quirk for ASUS AT5NM10T-I
  sched: Fix select_idle_sibling() regression in selecting an idle SMT sibling
  ...
2011-12-21 09:51:23 +01:00
MyungJoo Ham 7b40503811 PM/Devfreq: Add Exynos4-bus device DVFS driver for Exynos4210/4212/4412.
Exynos4-bus device devfreq driver add DVFS capability for
Exynos4210/4212/4412-Bus (memory). The driver monitors PPMU counters of memory
controllers and adjusts operating frequencies and voltages with OPP.
For Exynos4210, vdd_int is controlled. For exynos4412/4212, vdd_mif and
vdd_int are controlled.

Dependency (CONFIG_EXYNOS_ASV):
Exynos4 ASV driver has been posted in the mailing list; however, it
si not yet upstreamed. Although the current revision of Exynos4 ASV
patch does not contain "CONFIG_EXYNOS_ASV", we have added the symbol
to hide the dependent from compilers for now. As soon as Exynos4 ASV
drivers are merged, the #ifdef statement will be removed or the
name will be changed.

However, enabling ASV is essential in most Exynos4 chips to reduce
the power consumption of Exynos4210 because without ASV, this Devfreq
driver assumes the worst case scenario, which consumes more power.

Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>

---
Changes from v1
- Support 4212 and 4412 as well as 4210.
2011-12-20 14:08:08 +09:00
Axel Lin 3f19f08a7e PM / devfreq: separate error paths from successful path
I think this change improves code readability.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
2011-11-23 21:05:55 +01:00
MyungJoo Ham 6c81f90588 PM / devfreq: correct Kconfig dependency
Devfreq does not depend on OPP. The dependency is removed.

Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
2011-11-14 23:31:35 +01:00
Axel Lin 9f3bdd4f93 PM / devfreq: fix use after free in devfreq_remove_device
In devfreq_remove_device, calling _remove_devfreq will also free devfreq.
Don't dereference devfreq->governor->no_central_polling after _remove_devfreq.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
2011-11-14 23:31:29 +01:00
MyungJoo Ham 952f6d1386 PM / devfreq: Remove compiler error after irq.h update
Added <linux/module.h> and <linux/stat.h> to avoid a compiler error
because linux/irq.h no longer includes linux/module.h after Linux 3.2.

Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
2011-11-10 10:16:23 +01:00
MyungJoo Ham ce26c5bb95 PM / devfreq: Add basic governors
Four cpufreq-like governors are provided as examples.

powersave: use the lowest frequency possible. The user (device) should
set the polling_ms as 0 because polling is useless for this governor.

performance: use the highest freqeuncy possible. The user (device)
should set the polling_ms as 0 because polling is useless for this
governor.

userspace: use the user specified frequency stored at
devfreq.user_set_freq. With sysfs support in the following patch, a user
may set the value with the sysfs interface.

simple_ondemand: simplified version of cpufreq's ondemand governor.

When a user updates OPP entries (enable/disable/add), OPP framework
automatically notifies devfreq to update operating frequency
accordingly. Thus, devfreq users (device drivers) do not need to update
devfreq manually with OPP entry updates or set polling_ms for powersave
, performance, userspace, or any other "static" governors.

Note that these are given only as basic examples for governors and any
devices with devfreq may implement their own governors with the drivers
and use them.

Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Mike Turquette <mturquette@ti.com>
Acked-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
2011-10-02 00:19:34 +02:00
MyungJoo Ham 9005b65099 PM / devfreq: Add common sysfs interfaces
Device specific sysfs interface /sys/devices/.../power/devfreq_*
- governor	R: name of governor
- cur_freq	R: current frequency
- polling_interval	R: polling interval in ms given with devfreq profile
			W: update polling interval.
- central_polling	R: 1 if polling is managed by devfreq framework

Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Mike Turquette <mturquette@ti.com>
Acked-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
--
 Documentation/ABI/testing/sysfs-class-devfreq |   44 ++++++++++++++++
 drivers/devfreq/devfreq.c                     |   69 ++++++++++++++++++++++++++
 2 files changed, 113 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-class-devfreq
2011-10-02 00:19:28 +02:00
MyungJoo Ham a3c98b8b2e PM: Introduce devfreq: generic DVFS framework with device-specific OPPs
With OPPs, a device may have multiple operable frequency and voltage
sets. However, there can be multiple possible operable sets and a system
will need to choose one from them. In order to reduce the power
consumption (by reducing frequency and voltage) without affecting the
performance too much, a Dynamic Voltage and Frequency Scaling (DVFS)
scheme may be used.

This patch introduces the DVFS capability to non-CPU devices with OPPs.
DVFS is a techique whereby the frequency and supplied voltage of a
device is adjusted on-the-fly. DVFS usually sets the frequency as low
as possible with given conditions (such as QoS assurance) and adjusts
voltage according to the chosen frequency in order to reduce power
consumption and heat dissipation.

The generic DVFS for devices, devfreq, may appear quite similar with
/drivers/cpufreq.  However, cpufreq does not allow to have multiple
devices registered and is not suitable to have multiple heterogenous
devices with different (but simple) governors.

Normally, DVFS mechanism controls frequency based on the demand for
the device, and then, chooses voltage based on the chosen frequency.
devfreq also controls the frequency based on the governor's frequency
recommendation and let OPP pick up the pair of frequency and voltage
based on the recommended frequency. Then, the chosen OPP is passed to
device driver's "target" callback.

When PM QoS is going to be used with the devfreq device, the device
driver should enable OPPs that are appropriate with the current PM QoS
requests. In order to do so, the device driver may call opp_enable and
opp_disable at the notifier callback of PM QoS so that PM QoS's
update_target() call enables the appropriate OPPs. Note that at least
one of OPPs should be enabled at any time; be careful when there is a
transition.

Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Mike Turquette <mturquette@ti.com>
Acked-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
2011-10-02 00:19:15 +02:00