releases/2.6.27.15/cpuidle-use-last_state-which-can-reflect-the-actual-state-entered.patch

From trenn@suse.de  Tue Feb  3 14:54:29 2009
From: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Date: Tue, 27 Jan 2009 17:38:45 +0100
Subject: cpuidle: use last_state which can reflect the actual state entered
To: stable@kernel.org
Cc: Len Brown <len.brown@intel.com>, Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Message-ID: <1233074343-23414-4-git-send-email-trenn@suse.de>


From: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>

commit 887e301aa1105326f1412a98749024263b1031c7 upstream

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>
Tested-by: Kevin Hilman <khilman@deeprootsystems.com>
Signed-off-by: Len Brown <len.brown@intel.com>
Cc: Thomas Renninger <trenn@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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

--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -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++;