cpuidle: Single/Global registration of idle states

This patch makes the cpuidle_states structure global (single copy)
instead of per-cpu. The statistics needed on per-cpu basis
by the governor are kept per-cpu. This simplifies the cpuidle
subsystem as state registration is done by single cpu only.
Having single copy of cpuidle_states saves memory. Rare case
of asymmetric C-states can be handled within the cpuidle driver
and architectures such as POWER do not have asymmetric C-states.

Having single/global registration of all the idle states,
dynamic C-state transitions on x86 are handled by
the boot cpu. Here, the boot cpu  would disable all the devices,
re-populate the states and later enable all the devices,
irrespective of the cpu that would receive the notification first.

Reference:
https://lkml.org/lkml/2011/4/25/83

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, 2 insertions, 1 deletions

diff --git a/drivers/cpuidle/sysfs.c b/drivers/cpuidle/sysfs.c
index 8a1ace104476..1e756e160dca 100644
--- a/drivers/cpuidle/sysfs.c
+++ b/drivers/cpuidle/sysfs.c
@@ -322,13 +322,14 @@ int cpuidle_add_state_sysfs(struct cpuidle_device *device)
 {
         int i, ret = -ENOMEM;
         struct cpuidle_state_kobj *kobj;
+        struct cpuidle_driver *drv = cpuidle_get_driver();
 
         /* state statistics */
         for (i = 0; i < device->state_count; i++) {
                 kobj = kzalloc(sizeof(struct cpuidle_state_kobj), GFP_KERNEL);
                 if (!kobj)
                         goto error_state;
-                kobj->state = &device->states[i];
+                kobj->state = &drv->states[i];
                 kobj->state_usage = &device->states_usage[i];
                 init_completion(&kobj->kobj_unregister);