thermal: step_wise: fix: Prevent from binary overflow when trend is dropping

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@samsung.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Cc: Mason <slash.tmp@free.fr>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

diff --git a/drivers/thermal/step_wise.c b/drivers/thermal/step_wise.c
index ee52ab7d37301356e4386cc8f21151eade215e96..c501eba601da9c56f363f386e19ce758114230d1 100644 (file)
--- 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 {