[patch 1/2] cpuidle: use last_state which can reflect the actual state entered

[Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>]

[-- Attachment #1: cpuidle_proper_time_accounting.patch --]
[-- Type: text/plain, Size: 1338 bytes --]

cpuidle accounts the idle time for the C-state it was trying to enter and
not to the actual state that the driver eventually entered. The driver may
select a different state than the one chosen by cpuidle due to
constraints like bus-mastering, etc.

Change the time acounting code to look at the dev->last_state after
returning from target_state->enter(). Driver can modify dev->last_state
internally, inside the enter routine to reflect the actual C-state
entered.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>

---
 drivers/cpuidle/cpuidle.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

Index: tip/drivers/cpuidle/cpuidle.c
===================================================================
--- tip.orig/drivers/cpuidle/cpuidle.c	2008-09-23 13:52:59.000000000 -0700
+++ tip/drivers/cpuidle/cpuidle.c	2008-09-23 14:22:43.000000000 -0700
@@ -71,8 +71,11 @@ static void cpuidle_idle_call(void)
 	target_state = &dev->states[next_state];
 
 	/* enter the state and update stats */
-	dev->last_residency = target_state->enter(dev, target_state);
 	dev->last_state = target_state;
+	dev->last_residency = target_state->enter(dev, target_state);
+	if (dev->last_state)
+		target_state = dev->last_state;
+
 	target_state->time += (unsigned long long)dev->last_residency;
 	target_state->usage++;
 

--