Re: [PATCH 1/3][v3] Thermal: initialize thermal zone device correctly

[Eduardo Valentin <edubezval@gmail.com>]

For some reason, I thought Rui had picked this already. 

Anyways, here are a couple of comments:

On Fri, Oct 30, 2015 at 04:31:47PM +0800, Chen Yu wrote:
> From: Zhang Rui <rui.zhang@intel.com>
> 
> After thermal zone device registered, as we have not read any
> temperature before, thus tz->temperature should not be 0,
> which actually means 0C, and thermal trend is not available.
> In this case, we need specially handling for the first
> thermal_zone_device_update().
> 
> Both thermal core framework and step_wise governor is
> enhanced to handle this. And since the step_wise governor
> is the only one that uses trends, so it's the only thermal
> governor that needs to be updated.
> 
> CC: <stable@vger.kernel.org> #3.18+
> Tested-by: Manuel Krause <manuelkrause@netscape.net>
> Tested-by: szegad <szegadlo@poczta.onet.pl>
> Tested-by: prash <prash.n.rao@gmail.com>
> Tested-by: amish <ammdispose-arch@yahoo.com>
> Tested-by: Matthias <morpheusxyz123@yahoo.de>
> Reviewed-by: Javi Merino <javi.merino@arm.com>
> Signed-off-by: Zhang Rui <rui.zhang@intel.com>
> Signed-off-by: Chen Yu <yu.c.chen@intel.com>
> ---
>  drivers/thermal/step_wise.c    | 17 +++++++++++++++--
>  drivers/thermal/thermal_core.c | 19 +++++++++++++++++--
>  drivers/thermal/thermal_core.h |  1 +

I would prefer if you could split this patch in two. One for thermal
core another one for step wise.

>  include/linux/thermal.h        |  3 +++
>  4 files changed, 36 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/thermal/step_wise.c b/drivers/thermal/step_wise.c
> index 2f9f708..ea9366a 100644
> --- a/drivers/thermal/step_wise.c
> +++ b/drivers/thermal/step_wise.c
> @@ -63,6 +63,19 @@ static unsigned long get_target_state(struct thermal_instance *instance,
>  	next_target = instance->target;
>  	dev_dbg(&cdev->device, "cur_state=%ld\n", cur_state);
>  
> +	if (!instance->initialized) {
> +		if (throttle) {
> +			next_target = (cur_state + 1) >= instance->upper ?
> +					instance->upper :
> +					((cur_state + 1) < instance->lower ?
> +					instance->lower : (cur_state + 1));
> +		} else {
> +			next_target = THERMAL_NO_TARGET;
> +		}
> +
> +		return next_target;
> +	}
> +
>  	switch (trend) {
>  	case THERMAL_TREND_RAISING:
>  		if (throttle) {
> @@ -149,7 +162,7 @@ static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)
>  		dev_dbg(&instance->cdev->device, "old_target=%d, target=%d\n",
>  					old_target, (int)instance->target);
>  
> -		if (old_target == instance->target)
> +		if (instance->initialized && old_target == instance->target)
>  			continue;
>  
>  		/* Activate a passive thermal instance */
> @@ -161,7 +174,7 @@ static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)
>  			instance->target == THERMAL_NO_TARGET)
>  			update_passive_instance(tz, trip_type, -1);
>  
> -
> +		instance->initialized = true;
>  		instance->cdev->updated = false; /* cdev needs update */
>  	}
>  

Considering that I understood the problem and your proposal well, I
would say these changes on step wise are the perfect case for setting up
a step_wise.bind_to_tz(). bind_to_tz() is already designed as an
opportunity for governor to check the thermal zone status at the time of
binding. Remember that moving to bind_to_tz() covers not only
registration time, but governor switching too (say, user chooses
user_space, then step_wise).

The above code seams to be correct, but after reviewing the code
of step_wise.throttle(), I would say it is already complicated and
deserves simplification, when possible.



> diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
> index d9e525c..682bc1e 100644
> --- a/drivers/thermal/thermal_core.c
> +++ b/drivers/thermal/thermal_core.c
> @@ -532,8 +532,22 @@ static void update_temperature(struct thermal_zone_device *tz)
>  	mutex_unlock(&tz->lock);
>  
>  	trace_thermal_temperature(tz);
> -	dev_dbg(&tz->device, "last_temperature=%d, current_temperature=%d\n",
> -				tz->last_temperature, tz->temperature);
> +	if (tz->last_temperature == THERMAL_TEMP_INVALID)
> +		dev_dbg(&tz->device, "last_temperature N/A, current_temperature=%d\n",
> +			tz->temperature);
> +	else
> +		dev_dbg(&tz->device, "last_temperature=%d, current_temperature=%d\n",
> +			tz->last_temperature, tz->temperature);
> +}
> +
> +static void thermal_zone_device_reset(struct thermal_zone_device *tz)
> +{
> +	struct thermal_instance *pos;
> +
> +	tz->temperature = THERMAL_TEMP_INVALID;
> +	tz->passive = 0;
> +	list_for_each_entry(pos, &tz->thermal_instances, tz_node)
> +		pos->initialized = false;
>  }
>  
>  void thermal_zone_device_update(struct thermal_zone_device *tz)
> @@ -1900,6 +1914,7 @@ struct thermal_zone_device *thermal_zone_device_register(const char *type,
>  
>  	INIT_DELAYED_WORK(&(tz->poll_queue), thermal_zone_device_check);
>  
> +	thermal_zone_device_reset(tz);
>  	thermal_zone_device_update(tz);
>  
>  	return tz;
> diff --git a/drivers/thermal/thermal_core.h b/drivers/thermal/thermal_core.h
> index d7ac1fc..749d41a 100644
> --- a/drivers/thermal/thermal_core.h
> +++ b/drivers/thermal/thermal_core.h
> @@ -41,6 +41,7 @@ struct thermal_instance {
>  	struct thermal_zone_device *tz;
>  	struct thermal_cooling_device *cdev;
>  	int trip;
> +	bool initialized;
>  	unsigned long upper;	/* Highest cooling state for this trip point */
>  	unsigned long lower;	/* Lowest cooling state for this trip point */
>  	unsigned long target;	/* expected cooling state */
> diff --git a/include/linux/thermal.h b/include/linux/thermal.h
> index 157d366..5bcabc7 100644
> --- a/include/linux/thermal.h
> +++ b/include/linux/thermal.h
> @@ -43,6 +43,9 @@
>  /* Default weight of a bound cooling device */
>  #define THERMAL_WEIGHT_DEFAULT 0
>  
> +/* use value, which < 0K, to indicate an invalid/uninitialized temperature */
> +#define THERMAL_TEMP_INVALID	-274000
> +
>  /* Unit conversion macros */
>  #define KELVIN_TO_CELSIUS(t)	(long)(((long)t-2732 >= 0) ?	\
>  				((long)t-2732+5)/10 : ((long)t-2732-5)/10)
> -- 
> 1.8.4.2
>