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Subject: Re: [PATCH v2 02/11] thermal: add irq-mode configuration for trip
 point
From:   Lukasz Luba <l.luba@partner.samsung.com>
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
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Date:   Thu, 6 Dec 2018 20:55:05 +0100
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On 12/6/18 8:18 PM, Lukasz Luba wrote:
> 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.
Do you suggest to cover the 'case 1'?
It would be possible after adding a new enum THERMAL_FRAMEWORK_POLL, 
then function:
thermal_zone_device_check() will call
thermal_zone_device_update(tz, THERMAL_FRAMEWORK_POLL)
and in handle_thermal_trip() implement something like:
--------------8<----------------
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))
		return;

	if (tz->ops->get_trip_irq_mode)
		tz->ops->get_trip_irq_mode(tz, trip, &irq_mode)

	if (tz->notify_event == THERMAL_FRAMEWORK_POLL && irq_mode)
		return;
...

	if (!irq_mode)
		monitor_thermal_zone(tz);
}

---------->8-----------------------

I could implement it in v3 if you don't see that it add too much of mess 
and agree for this approach.

Regards,
Lukasz

> 
> 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 */
>>
>>