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, 17 insertions, 14 deletions

diff --git a/arch/arm/mach-at91/cpuidle.c b/arch/arm/mach-at91/cpuidle.c
index 4696a0d61e2e..93178f67420e 100644
--- a/arch/arm/mach-at91/cpuidle.c
+++ b/arch/arm/mach-at91/cpuidle.c
@@ -33,6 +33,7 @@ static struct cpuidle_driver at91_idle_driver = {
 
 /* Actual code that puts the SoC in different idle states */
 static int at91_enter_idle(struct cpuidle_device *dev,
+                        struct cpuidle_driver *drv,
                                int index)
 {
         struct timeval before, after;
@@ -64,27 +65,29 @@ static int at91_enter_idle(struct cpuidle_device *dev,
 static int at91_init_cpuidle(void)
 {
         struct cpuidle_device *device;
-
-        cpuidle_register_driver(&at91_idle_driver);
+        struct cpuidle_driver *driver = &at91_idle_driver;
 
         device = &per_cpu(at91_cpuidle_device, smp_processor_id());
         device->state_count = AT91_MAX_STATES;
+        driver->state_count = AT91_MAX_STATES;
 
         /* Wait for interrupt state */
-        device->states[0].enter = at91_enter_idle;
-        device->states[0].exit_latency = 1;
-        device->states[0].target_residency = 10000;
-        device->states[0].flags = CPUIDLE_FLAG_TIME_VALID;
-        strcpy(device->states[0].name, "WFI");
-        strcpy(device->states[0].desc, "Wait for interrupt");
+        driver->states[0].enter = at91_enter_idle;
+        driver->states[0].exit_latency = 1;
+        driver->states[0].target_residency = 10000;
+        driver->states[0].flags = CPUIDLE_FLAG_TIME_VALID;
+        strcpy(driver->states[0].name, "WFI");
+        strcpy(driver->states[0].desc, "Wait for interrupt");
 
         /* Wait for interrupt and RAM self refresh state */
-        device->states[1].enter = at91_enter_idle;
-        device->states[1].exit_latency = 10;
-        device->states[1].target_residency = 10000;
-        device->states[1].flags = CPUIDLE_FLAG_TIME_VALID;
-        strcpy(device->states[1].name, "RAM_SR");
-        strcpy(device->states[1].desc, "WFI and RAM Self Refresh");
+        driver->states[1].enter = at91_enter_idle;
+        driver->states[1].exit_latency = 10;
+        driver->states[1].target_residency = 10000;
+        driver->states[1].flags = CPUIDLE_FLAG_TIME_VALID;
+        strcpy(driver->states[1].name, "RAM_SR");
+        strcpy(driver->states[1].desc, "WFI and RAM Self Refresh");
+
+        cpuidle_register_driver(&at91_idle_driver);
 
         if (cpuidle_register_device(device)) {
                 printk(KERN_ERR "at91_init_cpuidle: Failed registering\n");