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

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Date:   Tue, 20 Nov 2018 16:38:33 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Wei Ni <wni@...dia.com>
Cc:     daniel.lezcano@...aro.org, linux-tegra@...r.kernel.org,
        rui.zhang@...el.com, edubezval@...il.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] thermal: tegra: add get_trend ops

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.

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().

Thierry

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