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Subject: Re: [PATCH] thermal: tegra: add get_trend ops
To:     Eduardo Valentin <edubezval@gmail.com>
CC:     Thierry Reding <thierry.reding@gmail.com>,
        <daniel.lezcano@linaro.org>, <linux-tegra@vger.kernel.org>,
        <rui.zhang@intel.com>, <linux-kernel@vger.kernel.org>
References: <1542705077-29697-1-git-send-email-wni@nvidia.com>
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From:   Wei Ni <wni@nvidia.com>
Message-ID: <f2d10339-4086-7102-9949-719483f545bf@nvidia.com>
Date:   Fri, 30 Nov 2018 11:07:42 +0800
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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@nvidia.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
>>>