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

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Date:   Wed, 5 Dec 2018 16:30:10 +0800
From:   Wei Ni <wni@...dia.com>
To:     Eduardo Valentin <edubezval@...il.com>
CC:     Thierry Reding <thierry.reding@...il.com>,
        <daniel.lezcano@...aro.org>, <linux-tegra@...r.kernel.org>,
        <rui.zhang@...el.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] thermal: tegra: add get_trend ops

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
>>>>