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: NNishanth Menon <nm@ti.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Governors compiled as modules may use these functions.
Signed-off-by: NMyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Use the value obtained from the function instead of -EINVAL.
Signed-off-by: NSachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: NMyungJoo Ham <myungjoo.ham@samsung.com>

'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: NSachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: NMyungJoo Ham <myungjoo.ham@samsung.com>

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: NKees Cook <keescook@chromium.org>
Signed-off-by: NMyungJoo Ham <myungjoo.ham@samsung.com>

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: NNishanth Menon <nm@ti.com>
Signed-off-by: NMyungJoo Ham <myungjoo.ham@samsung.com>

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: NNishanth Menon <nm@ti.com>
Acked-by: NMyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: NMyungJoo Ham <myungjoo.ham@samsung.com>

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: NNishanth Menon <nm@ti.com>
[Merge conflict resolved by MyungJoo Ham]
Signed-off-by: NMyungJoo Ham <myungjoo.ham@samsung.com>

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: NNishanth Menon <nm@ti.com>
Acked-by: NMyungJoo Ham <myungjoo.ham@samsung.com>

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: NNishanth Menon <nm@ti.com>
Acked-by: NMyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: NMyungJoo Ham <myungjoo.ham@samsung.com>

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: NJonghwa Lee <jonghwa3.lee@samsung.com>
[Added Documentation/ABI entry, updated kernel-doc, and resolved merge conflict]
Signed-off-by: NMyungJoo Ham <myungjoo.ham@samsung.com>

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: NNishanth Menon <nm@ti.com>
Signed-off-by: NMyungJoo Ham <myungjoo.ham@samsung.com>

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: NNishanth Menon <nm@ti.com>
Reviewed-by: NKevin Hilman <khilman@ti.com>
Acked-by: NMyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

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: NNishanth Menon <nm@ti.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

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: NNishanth Menon <nm@ti.com>
Acked-by: NMyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

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: NNishanth Menon <nm@ti.com>
Acked-by: NRandy Dunlap <rdunlap@xenotime.net>
Acked-by: NMyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

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: NRajagopal Venkat <rajagopal.venkat@linaro.org>
Acked-by: NMyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

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: NRajagopal Venkat <rajagopal.venkat@linaro.org>
Acked-by: NMyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

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: NRajagopal Venkat <rajagopal.venkat@linaro.org>
Acked-by: NMyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

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: NTejun Heo <tj@kernel.org>

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: NMyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: NKyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: NMike Turquette <mturquette@ti.com>
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

The frequency requested to devfreq device driver from devfreq governors
is restricted by min_freq and max_freq input.
Signed-off-by: NMyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: NKyungmin Park <kyungmin.park@samsung.com>

I think this change improves code readability.
Signed-off-by: NAxel Lin <axel.lin@gmail.com>
Acked-by: NMyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

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: NAxel Lin <axel.lin@gmail.com>
Acked-by: NMyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

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: NMyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: NKyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

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: NMyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: NKyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: NMike Turquette <mturquette@ti.com>
Acked-by: NKevin Hilman <khilman@ti.com>
Signed-off-by: NRafael 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

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: NMyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: NKyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: NMike Turquette <mturquette@ti.com>
Acked-by: NKevin Hilman <khilman@ti.com>
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>