linux-kernel - [PATCH 3.16.y-ckt 016/118] thermal: step_wise: fix: Prevent from binary overflow when trend is dropping

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Date:	Wed, 12 Aug 2015 09:55:18 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Lukasz Majewski <l.majewski@...sung.com>,
	Zhang Rui <rui.zhang@...el.com>, Mason <slash.tmp@...e.fr>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 016/118] thermal: step_wise: fix: Prevent from binary overflow when trend is dropping

3.16.7-ckt16 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Lukasz Majewski <l.majewski@...sung.com>

commit 26bb0e9a1a938ec98ee07aa76533f1a711fba706 upstream.

It turns out that some boards can have instance->lower greater than 0 and
when thermal trend is dropping it results with next_target equal to -1.

Since the next_target is defined as unsigned long it is interpreted as
0xFFFFFFFF and larger than instance->upper.
As a result the next_target is set to instance->upper which ramps up to
maximal cooling device target when the temperature is steadily decreasing.

Signed-off-by: Lukasz Majewski <l.majewski@...sung.com>
Signed-off-by: Zhang Rui <rui.zhang@...el.com>
Cc: Mason <slash.tmp@...e.fr>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 drivers/thermal/step_wise.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/thermal/step_wise.c b/drivers/thermal/step_wise.c
index ee52ab7d3730..c501eba601da 100644
--- a/drivers/thermal/step_wise.c
+++ b/drivers/thermal/step_wise.c
@@ -76,7 +76,7 @@ static unsigned long get_target_state(struct thermal_instance *instance,
 			next_target = instance->upper;
 		break;
 	case THERMAL_TREND_DROPPING:
-		if (cur_state == instance->lower) {
+		if (cur_state <= instance->lower) {
 			if (!throttle)
 				next_target = THERMAL_NO_TARGET;
 		} else {
--
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