linux-kernel - [PATCH 01/18] cpuidle: menu: fixed wrapping timers at 4.294 seconds

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Message-id: <c82cf78992a66bfa7f0c82aeb20ba6922127463b.1301724243.git.len.brown@intel.com>
Date:	Sat, 02 Apr 2011 02:22:43 -0400
From:	Len Brown <lenb@...nel.org>
To:	linux-pm@...ts.linux-foundation.org
Cc:	linux-kernel@...r.kernel.org, Tero Kristo <tero.kristo@...ia.com>,
	stable@...nel.org, Len Brown <len.brown@...el.com>
Subject: [PATCH 01/18] cpuidle: menu: fixed wrapping timers at 4.294 seconds

From: Tero Kristo <tero.kristo@...ia.com>

Cpuidle menu governor is using u32 as a temporary datatype for storing
nanosecond values which wrap around at 4.294 seconds. This causes errors
in predicted sleep times resulting in higher than should be C state
selection and increased power consumption. This also breaks cpuidle
state residency statistics.

cc: stable@...nel.org
Signed-off-by: Tero Kristo <tero.kristo@...ia.com>
Signed-off-by: Len Brown <len.brown@...el.com>
---
 drivers/cpuidle/governors/menu.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index f508690..c47f3d0 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -237,6 +237,7 @@ static int menu_select(struct cpuidle_device *dev)
 	unsigned int power_usage = -1;
 	int i;
 	int multiplier;
+	struct timespec t;
 
 	if (data->needs_update) {
 		menu_update(dev);
@@ -251,8 +252,9 @@ static int menu_select(struct cpuidle_device *dev)
 		return 0;
 
 	/* determine the expected residency time, round up */
+	t = ktime_to_timespec(tick_nohz_get_sleep_length());
 	data->expected_us =
-	    DIV_ROUND_UP((u32)ktime_to_ns(tick_nohz_get_sleep_length()), 1000);
+		t.tv_sec * USEC_PER_SEC + t.tv_nsec / NSEC_PER_USEC;
 
 
 	data->bucket = which_bucket(data->expected_us);
-- 
1.7.5.rc0

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