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Date:   Thu, 29 Nov 2018 09:01:46 -0800
From:   Eduardo Valentin <edubezval@gmail.com>
To:     Wei Ni <wni@nvidia.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
Subject: Re: [PATCH] thermal: tegra: add get_trend ops
Message-ID: <20181129170145.GG2688@localhost.localdomain>
References: <1542705077-29697-1-git-send-email-wni@nvidia.com>
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 <d510d768-452f-5f70-a9b6-37d6a63a56c9@nvidia.com>
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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. 

> 
> 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
> >