cpuidle: Move dev->last_residency update to driver enter routine; remove dev->last_state

Cpuidle governor only suggests the state to enter using the
governor->select() interface, but allows the low level driver to
override the recommended state. The actual entered state
may be different because of software or hardware demotion. Software
demotion is done by the back-end cpuidle driver and can be accounted
correctly. Current cpuidle code uses last_state field to capture the
actual state entered and based on that updates the statistics for the
state entered.

Ideally the driver enter routine should update the counters,
and it should return the state actually entered rather than the time
spent there. The generic cpuidle code should simply handle where
the counters live in the sysfs namespace, not updating the counters.

Reference:
https://lkml.org/lkml/2011/3/25/52

Signed-off-by: Deepthi Dharwar <deepthi@linux.vnet.ibm.com>
Signed-off-by: Trinabh Gupta <g.trinabh@gmail.com>
Tested-by: Jean Pihet <j-pihet@ti.com>
Reviewed-by: Kevin Hilman <khilman@ti.com>
Acked-by: Arjan van de Ven <arjan@linux.intel.com>
Acked-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 3 insertions, 4 deletions

diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
index b51629e15cfc..8da811bcdbdb 100644
--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -42,7 +42,7 @@ struct cpuidle_state {
         unsigned long long      time; /* in US */
 
         int (*enter)    (struct cpuidle_device *dev,
-                         struct cpuidle_state *state);
+                        int index);
 };
 
 /* Idle State Flags */
@@ -87,13 +87,12 @@ struct cpuidle_device {
         int                     state_count;
         struct cpuidle_state    states[CPUIDLE_STATE_MAX];
         struct cpuidle_state_kobj *kobjs[CPUIDLE_STATE_MAX];
-        struct cpuidle_state    *last_state;
 
         struct list_head        device_list;
         struct kobject          kobj;
         struct completion       kobj_unregister;
         void                    *governor_data;
-        struct cpuidle_state    *safe_state;
+        int                     safe_state_index;
 
         int (*prepare)          (struct cpuidle_device *dev);
 };
@@ -169,7 +168,7 @@ struct cpuidle_governor {
         void (*disable)         (struct cpuidle_device *dev);
 
         int  (*select)          (struct cpuidle_device *dev);
-        void (*reflect)         (struct cpuidle_device *dev);
+        void (*reflect)         (struct cpuidle_device *dev, int index);
 
         struct module           *owner;
 };