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>

1 files changed, 10 insertions, 24 deletions

diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
index 281c72a3b9d5..9cdffde74bb5 100644
--- a/include/linux/devfreq.h
+++ b/include/linux/devfreq.h
@@ -91,25 +91,18 @@ struct devfreq_dev_profile {
  *                      status of the device (load = busy_time / total_time).
  *                      If no_central_polling is set, this callback is called
  *                      only with update_devfreq() notified by OPP.
- * @init                Called when the devfreq is being attached to a device
- * @exit                Called when the devfreq is being removed from a
- *                      device. Governor should stop any internal routines
- *                      before return because related data may be
- *                      freed after exit().
- * @no_central_polling  Do not use devfreq's central polling mechanism.
- *                      When this is set, devfreq will not call
- *                      get_target_freq with devfreq_monitor(). However,
- *                      devfreq will call get_target_freq with
- *                      devfreq_update() notified by OPP framework.
+ * @event_handler       Callback for devfreq core framework to notify events
+ *                      to governors. Events include per device governor
+ *                      init and exit, opp changes out of devfreq, suspend
+ *                      and resume of per device devfreq during device idle.
  *
  * Note that the callbacks are called with devfreq->lock locked by devfreq.
  */
 struct devfreq_governor {
         const char name[DEVFREQ_NAME_LEN];
         int (*get_target_freq)(struct devfreq *this, unsigned long *freq);
-        int (*init)(struct devfreq *this);
-        void (*exit)(struct devfreq *this);
-        const bool no_central_polling;
+        int (*event_handler)(struct devfreq *devfreq,
+                                unsigned int event, void *data);
 };
 
 /**
@@ -124,18 +117,13 @@ struct devfreq_governor {
  * @nb          notifier block used to notify devfreq object that it should
  *              reevaluate operable frequencies. Devfreq users may use
  *              devfreq.nb to the corresponding register notifier call chain.
- * @polling_jiffies     interval in jiffies.
+ * @work        delayed work for load monitoring.
  * @previous_freq       previously configured frequency value.
- * @next_polling        the number of remaining jiffies to poll with
- *                      "devfreq_monitor" executions to reevaluate
- *                      frequency/voltage of the device. Set by
- *                      profile's polling_ms interval.
  * @data        Private data of the governor. The devfreq framework does not
  *              touch this.
- * @being_removed       a flag to mark that this object is being removed in
- *                      order to prevent trying to remove the object multiple times.
  * @min_freq    Limit minimum frequency requested by user (0: none)
  * @max_freq    Limit maximum frequency requested by user (0: none)
+ * @stop_polling         devfreq polling status of a device.
  *
  * This structure stores the devfreq information for a give device.
  *
@@ -153,17 +141,15 @@ struct devfreq {
         struct devfreq_dev_profile *profile;
         const struct devfreq_governor *governor;
         struct notifier_block nb;
+        struct delayed_work work;
 
-        unsigned long polling_jiffies;
         unsigned long previous_freq;
-        unsigned int next_polling;
 
         void *data; /* private data for governors */
 
-        bool being_removed;
-
         unsigned long min_freq;
         unsigned long max_freq;
+        bool stop_polling;
 };
 
 #if defined(CONFIG_PM_DEVFREQ)