linux-kernel - Re: [PATCH] thermal: step_wise: set throttle target within thermal instance limits

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Date:	Tue, 9 Apr 2013 13:17:28 -0400
From:	Eduardo Valentin <eduardo.valentin@...com>
To:	Andrew Bresticker <abrestic@...omium.org>
CC:	Eduardo Valentin <eduardo.valentin@...com>,
	Zhang Rui <rui.zhang@...el.com>, <linux-pm@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] thermal: step_wise: set throttle target within thermal
 instance limits

On 09-04-2013 13:09, Andrew Bresticker wrote:
> Hi Eduardo,
>
> On Tue, Apr 9, 2013 at 8:00 AM, Eduardo Valentin
> <eduardo.valentin@...com> wrote:
>> Hi Andrew,
>>
>>
>> On 08-04-2013 19:56, Andrew Bresticker wrote:
>>>
>>> When selecting a target cooling state in get_target_state(), make sure
>>> that the state is at least as high as the minimum when the temperature
>>> is rising and at least as low as the maximum when the temperature is
>>> falling.  Previously the cooling level would only be incremented or
>>> decremented by one in these cases.
>>>
>>> Signed-off-by: Andrew Bresticker <abrestic@...omium.org>
>>> ---
>>>    drivers/thermal/step_wise.c | 4 ++++
>>>    1 file changed, 4 insertions(+)
>>>
>>> diff --git a/drivers/thermal/step_wise.c b/drivers/thermal/step_wise.c
>>> index 0cd5e9f..49992a4 100644
>>> --- a/drivers/thermal/step_wise.c
>>> +++ b/drivers/thermal/step_wise.c
>>> @@ -47,9 +47,13 @@ static unsigned long get_target_state(struct
>>> thermal_instance *instance,
>>>          if (trend == THERMAL_TREND_RAISING) {
>>>                  cur_state = cur_state < instance->upper ?
>>>                              (cur_state + 1) : instance->upper;
>>> +               if (cur_state < instance->lower)
>>> +                       cur_state = instance->lower;
>>>          } else if (trend == THERMAL_TREND_DROPPING) {
>>>                  cur_state = cur_state > instance->lower ?
>>>                              (cur_state - 1) : instance->lower;
>>> +               if (cur_state > instance->upper)
>>> +                       cur_state = instance->upper;
>>>          }
>>
>>
>>
>> In which situations cur_state will be out of the [lower;upper] boundaries? I
>> mean at this point while temperature is rising, and we are rising the
>> cooling level, we should be already above lower (and vice-versa). Can you
>> please describe better the situation you are trying to cover/ that you have
>> identified?
>
> Suppose we hit a trip point which has bounds from 5 to 10, but
> cur_state is 0 because there has previously been no thermal
> throttling.  In that case, we would only go to level 1, even though
> the thermal instance specifies we should be between 5 and 10.  This
> patch would fix it so that we go directly to level 5 instead.
>
> I will resend this with a more descriptive commit message.

Thanks, I appreciate it.

>
>>
>>>
>>>          return cur_state;
>>>
>>
>
> Thanks,
> Andrew
>
>

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