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Subject: Re: [PATCH v2 02/11] thermal: add irq-mode configuration for trip
 point
To:     Zhang Rui <rui.zhang@intel.com>, devicetree@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org
Cc:     edubezval@gmail.com, daniel.lezcano@linaro.org, robh+dt@kernel.org,
        mark.rutland@arm.com, corbet@lwn.net, b.zolnierkie@samsung.com,
        krzk@kernel.org
From:   Lukasz Luba <l.luba@partner.samsung.com>
Message-ID: <2ac425fc-7c32-6e2f-7086-c14f85b0bbfd@partner.samsung.com>
Date:   Thu, 6 Dec 2018 20:18:46 +0100
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Hi Rui,

On 12/5/18 4:09 PM, Zhang Rui wrote:
> On 三, 2018-11-07 at 18:09 +0100, Lukasz Luba wrote:
>> This patch adds support irq mode in trip point.
>> When that flag is set in DT, there is no need for polling
>> in thermal framework. Crossing the trip point will rise an IRQ.
>> The naming convention for tip point 'type' can be confussing
>> and 'passive' (whic is passive cooling) might be interpretted
>> wrongly.
>>
>> This mechanism prevents from missue and adds explicit setting
>> for hardware which support interrupts for pre-configured temperature
>> threshold.
>>
>> Cc: Zhang Rui <rui.zhang@intel.com>
>> Cc: Eduardo Valentin <edubezval@gmail.com>
>> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
>> Signed-off-by: Lukasz Luba <l.luba@partner.samsung.com>
>> ---
>>   drivers/thermal/of-thermal.c   | 17 +++++++++++++++++
>>   drivers/thermal/thermal_core.c | 10 ++++++++--
>>   include/linux/thermal.h        |  5 +++++
>>   3 files changed, 30 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/thermal/of-thermal.c b/drivers/thermal/of-
>> thermal.c
>> index 4bfdb4a..1a75946a 100644
>> --- a/drivers/thermal/of-thermal.c
>> +++ b/drivers/thermal/of-thermal.c
>> @@ -312,6 +312,20 @@ static int of_thermal_get_trip_type(struct
>> thermal_zone_device *tz, int trip,
>>   	return 0;
>>   }
>>   
>> +static int
>> +of_thermal_get_trip_irq_mode(struct thermal_zone_device *tz, int
>> trip,
>> +			     bool *mode)
>> +{
>> +	struct __thermal_zone *data = tz->devdata;
>> +
>> +	if (trip >= data->ntrips || trip < 0)
>> +		return -EDOM;
>> +
>> +	*mode = data->trips[trip].irq_mode;
>> +
>> +	return 0;
>> +}
>> +
>>   static int of_thermal_get_trip_temp(struct thermal_zone_device *tz,
>> int trip,
>>   				    int *temp)
>>   {
>> @@ -394,6 +408,7 @@ static struct thermal_zone_device_ops
>> of_thermal_ops = {
>>   	.set_mode = of_thermal_set_mode,
>>   
>>   	.get_trip_type = of_thermal_get_trip_type,
>> +	.get_trip_irq_mode = of_thermal_get_trip_irq_mode,
>>   	.get_trip_temp = of_thermal_get_trip_temp,
>>   	.set_trip_temp = of_thermal_set_trip_temp,
>>   	.get_trip_hyst = of_thermal_get_trip_hyst,
>> @@ -827,6 +842,8 @@ static int thermal_of_populate_trip(struct
>> device_node *np,
>>   		return ret;
>>   	}
>>   
>> +	trip->irq_mode = of_property_read_bool(np, "irq-mode");
>> +
>>   	/* Required for cooling map matching */
>>   	trip->np = np;
>>   	of_node_get(np);
>> diff --git a/drivers/thermal/thermal_core.c
>> b/drivers/thermal/thermal_core.c
>> index 39fc812..6d41e08 100644
>> --- a/drivers/thermal/thermal_core.c
>> +++ b/drivers/thermal/thermal_core.c
>> @@ -406,6 +406,7 @@ static void handle_critical_trips(struct
>> thermal_zone_device *tz,
>>   static void handle_thermal_trip(struct thermal_zone_device *tz, int
>> trip)
>>   {
>>   	enum thermal_trip_type type;
>> +	bool irq_mode = false;
>>   
>>   	/* Ignore disabled trip points */
>>   	if (test_bit(trip, &tz->trips_disabled))
>> @@ -419,9 +420,14 @@ static void handle_thermal_trip(struct
>> thermal_zone_device *tz, int trip)
>>   		handle_non_critical_trips(tz, trip);
>>   	/*
>>   	 * Alright, we handled this trip successfully.
>> -	 * So, start monitoring again.
>> +	 * So, start monitoring in polling mode if
>> +	 * trip is not using irq HW support.
>>   	 */
>> -	monitor_thermal_zone(tz);
>> +	if (tz->ops->get_trip_irq_mode)
>> +		tz->ops->get_trip_irq_mode(tz, trip, &irq_mode);
>> +
>> +	if (!irq_mode)
>> +		monitor_thermal_zone(tz);
>>   }
>>   
> handle_thermal_trip() is called from thermal_zone_device_update(), and
> it is invoked for every trip points.
> say, you have a passive trip point 1 that supports irq_mode, and
> another passive trip point 2 that does not support irq_mode,
> monitor_thermal_zone() is still called in handle_thermal_trip(tz, 2),
> and the passive timer will be activated anyway, do I miss something?
Yes, the passive timer will be activated in your example. It is correct
behavior and does not break anything.
case 1: there is 'k' passive trip points which have irq_mode and 1
additional which does not have 'irq_mode', the framework will start
polling but skip check for those 'k' trip points.
case 2: all of the passive trip points have irq_mode set, the framework
will not register 'scheduled_work' because it will not call 
'monitor_thermal_zone()'.
This is the case of most Exynos platforms, but there is one exception 
which has 'case 1' with 2 trip points not supporting irq_mode.

Regards,
Lukasz

> 
> thanks,
> rui
> 
>>   static void update_temperature(struct thermal_zone_device *tz)
>> diff --git a/include/linux/thermal.h b/include/linux/thermal.h
>> index 5f4705f..b064565 100644
>> --- a/include/linux/thermal.h
>> +++ b/include/linux/thermal.h
>> @@ -103,6 +103,7 @@ struct thermal_zone_device_ops {
>>   		enum thermal_device_mode);
>>   	int (*get_trip_type) (struct thermal_zone_device *, int,
>>   		enum thermal_trip_type *);
>> +	int (*get_trip_irq_mode) (struct thermal_zone_device *, int,
>> bool *);
>>   	int (*get_trip_temp) (struct thermal_zone_device *, int, int
>> *);
>>   	int (*set_trip_temp) (struct thermal_zone_device *, int,
>> int);
>>   	int (*get_trip_hyst) (struct thermal_zone_device *, int, int
>> *);
>> @@ -196,6 +197,7 @@ struct thermal_zone_device {
>>   	struct thermal_attr *trip_temp_attrs;
>>   	struct thermal_attr *trip_type_attrs;
>>   	struct thermal_attr *trip_hyst_attrs;
>> +	struct thermal_attr *trip_irq_mode_attrs;
>>   	void *devdata;
>>   	int trips;
>>   	unsigned long trips_disabled;	/* bitmap for disabled
>> trips */
>> @@ -364,6 +366,8 @@ struct thermal_zone_of_device_ops {
>>    * @temperature: temperature value in miliCelsius
>>    * @hysteresis: relative hysteresis in miliCelsius
>>    * @type: trip point type
>> + * @irq_mode: to not use polling in framework set support of HW irq
>> (which will
>> + *	      be triggered when temperature reaches this level).
>>    */
>>   
>>   struct thermal_trip {
>> @@ -371,6 +375,7 @@ struct thermal_trip {
>>   	int temperature;
>>   	int hysteresis;
>>   	enum thermal_trip_type type;
>> +	bool irq_mode;
>>   };
>>   
>>   /* Function declarations */
> 
>