linux-kernel - [PATCH 1/3] thermal: step_wise: fix: Prevent from binary overflow when trend is dropping

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Message-id: <1411547232-21493-2-git-send-email-l.majewski@samsung.com>
Date:	Wed, 24 Sep 2014 10:27:10 +0200
From:	Lukasz Majewski <l.majewski@...sung.com>
To:	Zhang Rui <rui.zhang@...el.com>,
	Eduardo Valentin <edubezval@...il.com>
Cc:	Linux PM list <linux-pm@...r.kernel.org>,
	Lukasz Majewski <l.majewski@...ess.pl>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	linux-kernel@...r.kernel.org,
	Lukasz Majewski <l.majewski@...sung.com>
Subject: [PATCH 1/3] thermal: step_wise: fix: Prevent from binary overflow when
 trend is dropping

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>
---
 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 3b54c2c..fdd1f52 100644
--- a/drivers/thermal/step_wise.c
+++ b/drivers/thermal/step_wise.c
@@ -77,7 +77,7 @@ 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 {
-- 
2.0.0.rc2

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