Re: [PATCH V4 04/13] Thermal: Introduce .get_trend() callback.

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Thursday, July 26, 2012, Zhang Rui wrote:
> According to ACPI spec, tc1 and tc2 are used by OSPM
> to anticipate the temperature trends.
> We introduced the same concept to the generic thermal layer
> for passive cooling, but now it seems that these values
> are hard to be used on other platforms.
> 
> So We introduce .get_trend() as a more general solution.
> 
> For the platform thermal drivers that have their own way to
> anticipate the temperature trends, they should provide
> their own .get_trend() callback.
> Or else, we will calculate the temperature trends by simply
> comparing the current temperature and the cached previous
> temperature reading.

As far as the code is concerned:

Reviewed-by: Rafael J. Wysocki <rjw@sisk.pl>

I wonder, though, if there are any users of the thermal core currently in the
tree who should introduce their own .get_trend() callbacks?

Rafael


> Signed-off-by: Zhang Rui <rui.zhang@intel.com>
> ---
>  drivers/acpi/thermal.c        |   33 +++++++++++++++++++++++++++++++++
>  drivers/thermal/thermal_sys.c |   19 +++++++++++++++++--
>  include/linux/thermal.h       |    9 +++++++++
>  3 files changed, 59 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/acpi/thermal.c b/drivers/acpi/thermal.c
> index b48ec3e..0c49e42 100644
> --- a/drivers/acpi/thermal.c
> +++ b/drivers/acpi/thermal.c
> @@ -704,6 +704,38 @@ static int thermal_get_crit_temp(struct thermal_zone_device *thermal,
>  		return -EINVAL;
>  }
>  
> +static int thermal_get_trend(struct thermal_zone_device *thermal,
> +				int trip, enum thermal_trend *trend)
> +{
> +	struct acpi_thermal *tz = thermal->devdata;
> +	enum thermal_trip_type type;
> +	int i;
> +
> +	if (thermal_get_trip_type(thermal, trip, &type))
> +		return -EINVAL;
> +
> +	/* Only PASSIVE trip points need TREND */
> +	if (type != THERMAL_TRIP_PASSIVE)
> +		return -EINVAL;
> +
> +	/*
> +	 * tz->temperature has already been updated by generic thermal layer,
> +	 * before this callback being invoked
> +	 */
> +	i = (tz->trips.passive.tc1 * (tz->temperature - tz->last_temperature))
> +		+ (tz->trips.passive.tc2
> +		* (tz->temperature - tz->trips.passive.temperature));
> +
> +	if (i > 0)
> +		*trend = THERMAL_TREND_RAISING;
> +	else if (i < 0)
> +		*trend = THERMAL_TREND_DROPPING;
> +	else
> +		*trend = THERMAL_TREND_STABLE;
> +	return 0;
> +}
> +
> +
>  static int thermal_notify(struct thermal_zone_device *thermal, int trip,
>  			   enum thermal_trip_type trip_type)
>  {
> @@ -836,6 +868,7 @@ static const struct thermal_zone_device_ops acpi_thermal_zone_ops = {
>  	.get_trip_type = thermal_get_trip_type,
>  	.get_trip_temp = thermal_get_trip_temp,
>  	.get_crit_temp = thermal_get_crit_temp,
> +	.get_trend = thermal_get_trend,
>  	.notify = thermal_notify,
>  };
>  
> diff --git a/drivers/thermal/thermal_sys.c b/drivers/thermal/thermal_sys.c
> index 62b4279..68c93d4 100644
> --- a/drivers/thermal/thermal_sys.c
> +++ b/drivers/thermal/thermal_sys.c
> @@ -723,6 +723,20 @@ static void thermal_zone_device_passive(struct thermal_zone_device *tz,
>  	struct thermal_cooling_device *cdev;
>  	long state, max_state;
>  
> +	if (!tz->ops->get_trend ||
> +	    tz->ops->get_trend(tz, trip, (enum thermal_trend *)&trend)) {
> +		/*
> +		 * compare the current temperature and previous temperature
> +		 * to get the thermal trend, if no special requirement
> +		 */
> +		if (tz->temperature > tz->last_temperature)
> +			trend = THERMAL_TREND_RAISING;
> +		else if (tz->temperature < tz->last_temperature)
> +			trend = THERMAL_TREND_DROPPING;
> +		else
> +			trend = THERMAL_TREND_STABLE;
> +	}
> +
>  	/*
>  	 * Above Trip?
>  	 * -----------
> @@ -1091,6 +1105,9 @@ void thermal_zone_device_update(struct thermal_zone_device *tz)
>  		goto leave;
>  	}
>  
> +	tz->last_temperature = tz->temperature;
> +	tz->temperature = temp;
> +
>  	for (count = 0; count < tz->trips; count++) {
>  		tz->ops->get_trip_type(tz, count, &trip_type);
>  		tz->ops->get_trip_temp(tz, count, &trip_temp);
> @@ -1150,8 +1167,6 @@ void thermal_zone_device_update(struct thermal_zone_device *tz)
>  		thermal_zone_device_passive(tz, temp, tz->forced_passive,
>  					    THERMAL_TRIPS_NONE);
>  
> -	tz->last_temperature = temp;
> -
>  leave:
>  	if (tz->passive)
>  		thermal_zone_device_set_polling(tz, tz->passive_delay);
> diff --git a/include/linux/thermal.h b/include/linux/thermal.h
> index a43b12c..a01e3e6 100644
> --- a/include/linux/thermal.h
> +++ b/include/linux/thermal.h
> @@ -44,6 +44,12 @@ enum thermal_trip_type {
>  	THERMAL_TRIP_CRITICAL,
>  };
>  
> +enum thermal_trend {
> +	THERMAL_TREND_STABLE, /* temperature is stable */
> +	THERMAL_TREND_RAISING, /* temperature is raising */
> +	THERMAL_TREND_DROPPING, /* temperature is dropping */
> +};
> +
>  struct thermal_zone_device_ops {
>  	int (*bind) (struct thermal_zone_device *,
>  		     struct thermal_cooling_device *);
> @@ -65,6 +71,8 @@ struct thermal_zone_device_ops {
>  	int (*set_trip_hyst) (struct thermal_zone_device *, int,
>  			      unsigned long);
>  	int (*get_crit_temp) (struct thermal_zone_device *, unsigned long *);
> +	int (*get_trend) (struct thermal_zone_device *, int,
> +			  enum thermal_trend *);
>  	int (*notify) (struct thermal_zone_device *, int,
>  		       enum thermal_trip_type);
>  };
> @@ -111,6 +119,7 @@ struct thermal_zone_device {
>  	int tc2;
>  	int passive_delay;
>  	int polling_delay;
> +	int temperature;
>  	int last_temperature;
>  	bool passive;
>  	unsigned int forced_passive;
>