cpuidle: remove state_count field from struct cpuidle_device

Thomas Schlichter reports the following issue on his Samsung NC20:

"The C-states C1 and C2 to the OS when connected to AC, and additionally
provides the C3 C-state when disconnected from AC. However, the number
of C-states shown in sysfs is fixed to the number of C-states present
at boot.
If I boot with AC connected, I always only see the C-states up to C2
even if I disconnect AC.

The reason is commit 130a5f692425 (ACPI / cpuidle: remove dev->state_count
setting). It removes the update of dev->state_count, but sysfs uses
exactly this variable to show the C-states.

The fix is to use drv->state_count in sysfs. As this is currently the
last user of dev->state_count, this variable can be completely removed."

Remove dev->state_count as per the above.

Reported-by: Thomas Schlichter <[e-mail]>
Signed-off-by: Bartlomiej Zolnierkiewicz <[e-mail]>
Signed-off-by: Kyungmin Park <[e-mail]>
Acked-by: Daniel Lezcano <[e-mail]>
Cc: 3.14+ <[e-mail]> # 3.14+
[ rjw: Changelog ]
Signed-off-by: Rafael J. Wysocki <[e-mail]>

drivers/cpuidle/cpuidle.c

···
 	if (!dev->registered)
 		return -EINVAL;
 
-	if (!dev->state_count)
-		dev->state_count = drv->state_count;
-
 	ret = cpuidle_add_device_sysfs(dev);
 	if (ret)
 		return ret;

drivers/cpuidle/sysfs.c

···
 	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(device);
 
 	/* state statistics */
-	for (i = 0; i < device->state_count; i++) {
+	for (i = 0; i < drv->state_count; i++) {
 		kobj = kzalloc(sizeof(struct cpuidle_state_kobj), GFP_KERNEL);
 		if (!kobj)
 			goto error_state;
···
  */
 static void cpuidle_remove_state_sysfs(struct cpuidle_device *device)
 {
+	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(device);
 	int i;
 
-	for (i = 0; i < device->state_count; i++)
+	for (i = 0; i < drv->state_count; i++)
 		cpuidle_free_state_kobj(device, i);
 }
 

include/linux/cpuidle.h

···
 	unsigned int		cpu;
 
 	int			last_residency;
-	int			state_count;
 	struct cpuidle_state_usage	states_usage[CPUIDLE_STATE_MAX];
 	struct cpuidle_state_kobj *kobjs[CPUIDLE_STATE_MAX];
 	struct cpuidle_driver_kobj *kobj_driver;