linux-kernel - Re: [PATCH] thermal: tegra: add get

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Date:   Tue, 11 Dec 2018 14:20:00 +0800
From:   Wei Ni <wni@...dia.com>
To:     Eduardo Valentin <edubezval@...il.com>,
        <daniel.lezcano@...aro.org>, <rui.zhang@...el.com>
CC:     Thierry Reding <thierry.reding@...il.com>,
        <linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] thermal: tegra: add get_trend ops

Hi Rui & Eduardo,
Could you please take this patch?

Thanks.
Wei.

On 5/12/2018 4:30 PM, Wei Ni wrote:
> Hi Daniel,
> It seems no more comments, could this patch be approved?
> 
> Thanks.
> Wei.
> 
> On 30/11/2018 11:07 AM, Wei Ni wrote:
>>
>>
>> On 30/11/2018 1:01 AM, Eduardo Valentin wrote:
>>> On Wed, Nov 21, 2018 at 02:36:10PM +0800, Wei Ni wrote:
>>>>
>>>>
>>>> On 20/11/2018 11:38 PM, Thierry Reding wrote:
>>>>> On Tue, Nov 20, 2018 at 05:11:17PM +0800, Wei Ni wrote:
>>>>>> Add support for get_trend ops that allows soctherm
>>>>>> sensors to be used with the step-wise governor.
>>>>>>
>>>>>> Signed-off-by: Wei Ni <wni@...dia.com>
>>>>>> ---
>>>>>>  drivers/thermal/tegra/soctherm.c | 34 ++++++++++++++++++++++++++++++++++
>>>>>>  1 file changed, 34 insertions(+)
>>>>>>
>>>>>> diff --git a/drivers/thermal/tegra/soctherm.c b/drivers/thermal/tegra/soctherm.c
>>>>>> index ed28110a3535..d2951fbe2b7c 100644
>>>>>> --- a/drivers/thermal/tegra/soctherm.c
>>>>>> +++ b/drivers/thermal/tegra/soctherm.c
>>>>>> @@ -488,9 +488,43 @@ static int tegra_thermctl_set_trip_temp(void *data, int trip, int temp)
>>>>>>  	return 0;
>>>>>>  }
>>>>>>  
>>>>>> +static int tegra_thermctl_get_trend(void *data, int trip,
>>>>>> +				    enum thermal_trend *trend)
>>>>>> +{
>>>>>> +	struct tegra_thermctl_zone *zone = data;
>>>>>> +	struct thermal_zone_device *tz = zone->tz;
>>>>>> +	int trip_temp, temp, last_temp, ret;
>>>>>> +
>>>>>> +	if (!tz)
>>>>>> +		return -EINVAL;
>>>>>> +
>>>>>> +	ret = tz->ops->get_trip_temp(zone->tz, trip, &trip_temp);
>>>>>> +	if (ret)
>>>>>> +		return ret;
>>>>>> +
>>>>>> +	mutex_lock(&tz->lock);
>>>>>> +	temp = tz->temperature;
>>>>>> +	last_temp = tz->last_temperature;
>>>>>> +	mutex_unlock(&tz->lock);
>>>>>> +
>>>>>> +	if (temp > trip_temp) {
>>>>>> +		if (temp >= last_temp)
>>>>>> +			*trend = THERMAL_TREND_RAISING;
>>>>>> +		else
>>>>>> +			*trend = THERMAL_TREND_STABLE;
>>>>>> +	} else if (temp < trip_temp) {
>>>>>> +		*trend = THERMAL_TREND_DROPPING;
>>>>>> +	} else {
>>>>>> +		*trend = THERMAL_TREND_STABLE;
>>>>>> +	}
>>>>>> +
>>>>>> +	return 0;
>>>>>> +}
>>>>>
>>>>> This looks like a reimplementation of the get_tz_trend() helper. Is
>>>>> seems like that helper already has everything we need. Perhaps this
>>>>> isn't working because of-thermal installs of_thermal_get_trend(), a
>>>>> function that returns -EINVAL if the driver doesn't implement the
>>>>> ->get_trend() callback.
>>>>
>>>> 1. The get_tz_trend() helper can work, because it has:
>>>> if (tz->emul_temperature || !tz->ops->get_trend ||
>>>>             tz->ops->get_trend(tz, trip, &trend)) {
>>>> ...
>>>> }
>>>> the tz->ops->get_trend is of_thermal_get_trend(). If without special
>>>> get_trend(), it will return -EINVAL, so it will implement the if block
>>>> to get the "trend". If we have the special get_trend(), then the
>>>> of_thermal_get_trend() will return 0, so this helper will not implement
>>>> the if block, it will get the "trend" from the special get_trend().
>>>
>>> The idea of the helper is to provide a trend in case drivers dont have
>>> a specific way of doing so. 
>>
>> Yes, thanks for your explanation.
>>
>>>
>>>>
>>>> 2. There has a little difference between the helper and our special
>>>> callback. The tegra_thermctl_get_trend() consider the trip_temp, but the
>>>> get_tz_trend() helper didn't.
>>>>
>>>
>>> Yeah, if you are computing trend towards a trip, then yes, that is
>>> different and this patch is needed.
>>>
>>>>>
>>>>> Perhaps a better way would be to do something like this in
>>>>> thermal_zone_of_add_sensor():
>>>>>
>>>>> 	if (ops->get_trend)
>>>>> 		tzd->ops->get_trend = of_thermal_get_trend;
>>>>>
>>>>> That's similar to how ->set_trips() and ->set_emul_temp() are set up
>>>>> and should make sure that get_tz_trend() will do the right thing for
>>>>> all drivers that don't implement a special ->get_trend().
>>>>
>>>> As above description, I think the of_thermal_get_trend() already can
>>>> handle this case, doesn't need to change.
>>>>
>>>> Wei.
>>>>
>>>>>
>>>>> Thierry
>>>>>