Re: Requesting inclusion of 26bb0e9a in linux-3.14.y

[Luis Henriques <luis.henriques@canonical.com>]

On Tue, Jul 21, 2015 at 01:41:09PM +0200, Mason wrote:
> Hello,
> 
> This is my first time requesting inclusion of a patch, please
> point out any breach of protocol.
> 
> I'm using linux-3.14.y and I've run into a bug fixed in later
> kernel versions:
>

Thanks, I'm queuing this patch for the 3.16 kernel as well.

Cheers,
--
Luís

> commit 26bb0e9a1a938ec98ee07aa76533f1a711fba706
> Author: Lukasz Majewski <l.majewski@samsung.com>
> Date:   Wed Sep 24 10:27:10 2014 +0200
> 
>     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@samsung.com>
>     Signed-off-by: Zhang Rui <rui.zhang@intel.com>
> 
> diff --git a/drivers/thermal/step_wise.c b/drivers/thermal/step_wise.c
> index f251521baaa2..6705a0d746b3 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 {
> 
> 
> 
> 
> Here's the debug output on my board:
> 
> [   21.301211] thermal thermal_zone0: last_temperature=0, current_temperature=51000
> [   21.308803] thermal thermal_zone0: Trip0[type=1,temp=70000]:trend=1,throttle=0
> [   21.316248] thermal cooling_device0: cur_state=0
> [   21.320957] thermal cooling_device0: old_target=-1, target=-1
> [   21.326755] thermal cooling_device0: zone0->target=4294967295
> [   21.332544] thermal cooling_device0: set to state 0
> 
> [   34.349747] thermal thermal_zone0: last_temperature=51000, current_temperature=46000
> [   34.357830] thermal thermal_zone0: Trip0[type=1,temp=70000]:trend=2,throttle=0
> [   34.365254] thermal cooling_device0: cur_state=0
> [   34.369989] thermal cooling_device0: old_target=-1, target=4
> [   34.375740] thermal cooling_device0: zone0->target=4
> [   34.380867] thermal cooling_device0: set to state 4
> 
> Bug: raising the cooling state, despite the temperature dropping.
> 
> The .bind() call was
> 
>   thermal_zone_bind_cooling_device(tz, 0, cdev, 4, 1);
> 
> (The intent being that, once the system is above the trip temp,
> at least a little bit of cooling should be applied, always.)
> 
> cur_state = 0 is not equal to lower_state = 1
> 
> AFAICT, Lukasz's patch fixes that issue.
> 
> Regards.
> --
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