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time_in_state in struct devfreq is defined as unsigned long, so
devm_kzalloc should use sizeof(unsigned long) as argument instead
of sizeof(unsigned int), otherwise it will cause unexpected result
in 64bit system.
Signed-off-by: Xiaolong Ye <yexl@marvell.com>
Signed-off-by: Kevin Liu <kliu5@marvell.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
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The thermal infrastructure should use the devfreq cooling device, which
uses the OPP library to disable OPPs as necessary.
Fix a couple of typos in the same comment while we are at it.
Signed-off-by: Javi Merino <javi.merino@arm.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
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IS_ERR(_OR_NULL) already contain an 'unlikely' compiler flag and there
is no need to do that again from its callers. Drop it.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
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_remove_devfreq() does not have @skip anymore after 3.16.
The comment for _remove_devfreq() has been updated correspondingly.
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
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These functions are indended for use by drivers and should be available
also when the driver is built as a module.
Cc: MyungJoo Ham <myungjoo.ham@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Ãrjan Eide <orjan.eide@arm.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
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This patch add resource-managed function for devfreq opp as following
functions. The devm_devfreq_register_opp_notifier() manages automatically
the registration of devfreq opp using device resource management.
- devm_devfreq_register_opp_notifier
- devm_devfreq_unregister_opp_notifier()
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
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This patch add resource-managed function for devfreq device as following
functions. The devm_devfreq_add_device() manages automatically the memory
of devfreq device using device resource management.
- devm_devfreq_add_device()
- devm_devfreq_remove_device()
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
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resource free
This patch modify devfreq_remove_device() to improve the sequence of resource
free. If executing existing devfreq_remove_device(), this function always
executes _remove_devfreq() twice. In result, second _remove_devfreq() always
return error value. So, This patch resolves complicated function sequence
as following:
[Flow sequence before modification]
devfreq_remove_device()
_remove_devfreq(devfreq, false)
kfree(devfreq); /* Free devfreq */
if (!skip ...) { /* skip is false */
device_unregister(&devfreq->dev)
put_device(&devfreq->dev);
...
dev->release()
devfreq_dev_release()
_remove_devfreq(devfreq, true) <- Recall to free devfreq
/*
* Always return error without freeing resource because
* already _remove_devfreq() frees the memory of devfreq.
*/
}
[Flow sequence after modification]
devfreq_remove_device
device_unregister(&devfreq->dev)
put_device(&devfreq->dev);
..
dev->release()
devfreq_dev_release()
_remove_devfreq()
kfree(devfreq); /* Free devfreq */
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
[Merge conflict resolved by MyungJoo]
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
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The current devfreq_update_status() has the following bugs:
- If previous frequency doesn't have a valid level, it does an out of bounds
access into the trans_table and causes memory corruption.
- When the new frequency doesn't have a valid level, the time spent in the
new frequency is counted towards the next valid frequency switch instead of
being ignored.
- The time spent on the previous frequency is added to the new frequency's
stats instead of the previous frequency's stats.
This patch fixes all of this.
Signed-off-by: Saravana Kannan <skannan@codeaurora.org>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
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* pm-devfreq:
PM / devfreq: create_freezable_workqueue() doesn't return an ERR_PTR
PM / devfreq: Remove duplicate header file inclusion in exynos5_bus.c
PM / devfreq: Use devm_* APIs in exynos5_bus.c
PM / devfreq: Remove redundant platform_set_drvdata() in exynos5_bus.c
PM / devfreq: Fix incorrect usage of IS_ERR_OR_NULL in exynos5_bus.c
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The create_freezable_workqueue() function returns a NULL on error and
not an ERR_PTR.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
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Since Operating Performance Points (OPP) functions are specific
to device specific power management, be specific and rename opp.h
to pm_opp.h
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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Since Operating Performance Points (OPP) data structures are specific
to device specific power management, be specific and rename opp_* data
structures in OPP library with dev_pm_opp_* equivalent.
Affected structures are:
struct opp
enum opp_event
Minor checkpatch warning resulting of this change was fixed as well.
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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Since Operating Performance Points (OPP) functions are specific to
device specific power management, be specific and rename opp_*
accessors in OPP library with dev_pm_opp_* equivalent.
Affected functions are:
opp_get_voltage
opp_get_freq
opp_get_opp_count
opp_find_freq_exact
opp_find_freq_floor
opp_find_freq_ceil
opp_add
opp_enable
opp_disable
opp_get_notifier
opp_init_cpufreq_table
opp_free_cpufreq_table
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Nishanth Menon <nm@ti.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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The dev_attrs field of struct class is going away soon, dev_groups
should be used instead. This converts the devfreq_class code to use the
correct field.
Cc: MyungJoo Ham <myungjoo.ham@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Merge first patch-bomb from Andrew Morton:
- various misc bits
- I'm been patchmonkeying ocfs2 for a while, as Joel and Mark have been
distracted. There has been quite a bit of activity.
- About half the MM queue
- Some backlight bits
- Various lib/ updates
- checkpatch updates
- zillions more little rtc patches
- ptrace
- signals
- exec
- procfs
- rapidio
- nbd
- aoe
- pps
- memstick
- tools/testing/selftests updates
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (445 commits)
tools/testing/selftests: don't assume the x bit is set on scripts
selftests: add .gitignore for kcmp
selftests: fix clean target in kcmp Makefile
selftests: add .gitignore for vm
selftests: add hugetlbfstest
self-test: fix make clean
selftests: exit 1 on failure
kernel/resource.c: remove the unneeded assignment in function __find_resource
aio: fix wrong comment in aio_complete()
drivers/w1/slaves/w1_ds2408.c: add magic sequence to disable P0 test mode
drivers/memstick/host/r592.c: convert to module_pci_driver
drivers/memstick/host/jmb38x_ms: convert to module_pci_driver
pps-gpio: add device-tree binding and support
drivers/pps/clients/pps-gpio.c: convert to module_platform_driver
drivers/pps/clients/pps-gpio.c: convert to devm_* helpers
drivers/parport/share.c: use kzalloc
Documentation/accounting/getdelays.c: avoid strncpy in accounting tool
aoe: update internal version number to v83
aoe: update copyright date
aoe: perform I/O completions in parallel
...
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Calling dev_set_name with a single paramter causes it to be handled as a
format string. Many callers are passing potentially dynamic string
content, so use "%s" in those cases to avoid any potential accidents,
including wrappers like device_create*() and bdi_register().
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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- Added missing ABI documents
- Added comments to clarify the objectives of functions
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Acked-by: Nishanth Menon <nm@ti.com>
Acked-by: Rajagopal Venkat <rajagopal.venkat@linaro.org>
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devfreq stats is not taking device suspend and resume into
account. Fix it.
Signed-off-by: Rajagopal Venkat <rajagopal.venkat@linaro.org>
Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com>
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OPP pointers are protected by RCU locks, the pointer validity is
permissible only under the section of rcu_read_lock to rcu_read_unlock
Add documentation to the effect.
Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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* pm-devfreq: (23 commits)
PM / devfreq: remove compiler error with module governors (2)
PM / devfreq: Fix return value in devfreq_remove_governor()
PM / devfreq: Fix incorrect argument in error message
PM / devfreq: missing rcu_read_lock() added for find_device_opp()
PM / devfreq: remove compiler error when a governor is module
PM / devfreq: exynos4_bus.c: Fixed an alignment of the func call args.
PM / devfreq: Add sysfs node to expose available governors
PM / devfreq: allow sysfs governor node to switch governor
PM / devfreq: governors: add GPL module license and allow module build
PM / devfreq: map devfreq drivers to governor using name
PM / devfreq: register governors with devfreq framework
PM / devfreq: provide hooks for governors to be registered
PM / devfreq: export update_devfreq
PM / devfreq: Add sysfs node for representing frequency transition information.
PM / devfreq: Add sysfs node to expose available frequencies
PM / devfreq: documentation cleanups for devfreq header
PM / devfreq: Use devm_* functions in exynos4_bus.c
PM / devfreq: make devfreq_class static
PM / devfreq: fix sscanf handling for writable sysfs entries
PM / devfreq: kernel-doc typo corrections
...
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Governors compiled as modules may use these functions.
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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Use the value obtained from the function instead of -EINVAL.
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
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'g' is cast to the error return code. Hence gives the following error
which is fixed by this patch.
drivers/devfreq/devfreq.c:645 devfreq_remove_governor() error:
'g' dereferencing possible ERR_PTR()
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
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opp_get_notifier() uses find_device_opp(), which requires to
held rcu_read_lock. In order to keep the notifier-header
valid, we have added rcu_read_lock().
Reported-by: Kees Cook <keescook@chromium.org>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
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Now that governor list can be variable, knowing the available governors
is useful to be able to select a governor using relevant sysfs node.
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>
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This allows us to select governor runtime from the
default configuration without having to rebuild kernel
or the devfreq driver using the sysfs node:
/sys/class/devfreq/.../governor
cat of the governor will return valid governor
and an echo 'governor_name'>governor will switch
governor
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>
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Allow devfreq drivers to register a preferred governor name
and when the devfreq governor loads itself at a later point
required drivers are managed appropriately, at the time of
unload of a devfreq governor, stop managing those drivers
as well.
Since the governor structures do not need to be exposed
anymore, remove the definitions and make them static
NOTE: devfreq_list_lock is now used to protect governor
start and stop - as this allows us to protect governors and
devfreq with the proper dependencies as needed.
As part of this change, change the registration of exynos
bus driver to request for ondemand using the governor name.
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>
[Merge conflict resolved by MyungJoo Ham]
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
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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>
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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>
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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>
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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>
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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>
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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>
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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>
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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>
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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>
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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>
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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>
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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>
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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>
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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>
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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>
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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>
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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>
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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
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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>
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