Re: [PATCH v2 3/4] thermal: of: Extend of-thermal to export table of trip points

navneet kumar
2014-11-26T20:42:55Z

Hi Eduardo, Lukasz,

[Combining my concerns as a single text blob here]

I. Firstly, with the current patch
1. is it really needed to duplicate the struct thermal_trip? Why don’t
we get rid of the __thermal_trip and stay with the 'thermal_trip' ? it
is not a big change.

2. gtrips is not updated on "set_trip_temp" etc. actions via sysfs. (am
I missing something?).

II. The other concern is more of a design question
1. Do we intend to keep the of-thermal as a middle layer between the
thermal_core and the sensor device? OR, is the role of of-thermal just
to parse the DT and opt out ? currently of-thermal is somewhat a hybrid
of these as, in addition to parsing the dt, it holds on to the data
related to trip points etc. etc.

2. assuming latter is true (OF is just a dt parser helper): we should
not be adding more intelligence and dependencies linked to the OF.

3. assuming former is true (OF is a well-defined middle layer): All is
good till the point OF maintains the trip points (which is a good thing
since, OF caches on to the data); BUT, if we expose this information to
the sensor device too (as this patch is doing),

3a. we violate the layering principle :-)

3b. more importantly, this is all just excessive logic that we
put in which *could be useful* only if we intend to extend the
role of OF as a trip point management layer that does more than
just holding on to the data. This may include -

-> The sensor devices to know nothing about the
trip_points, instead the sensor devices would work on
"temperature thresholds" and OF would map sensor
thresholds to the actual trip points as needed
(configured from DT); while the sensor devices stick to
using "thresholds".

-> Queuing from above, sensors, most of the time, only
need to know a high and a low temp threshold; which
essentially is a subset of the active/passive etc. trip
points. Calculation of that based on the current temp,
as of today is replicated across all the sensor drivers
and can be hoisted up to the of-thermal.

Seems like this is the opportune time to make a call about the role of of-thermal?

On 11/26/2014 07:18 AM, Eduardo Valentin wrote:
> * PGP Signed by an unknown key
>
> Hello,
>
> On Wed, Nov 26, 2014 at 09:35:10AM +0100, Lukasz Majewski wrote:
>> Hi Eduardo,
>>
>>> Hello Lukasz,
>>>
>>> On Thu, Nov 20, 2014 at 05:21:27PM +0100, Lukasz Majewski wrote:
>>>> This patch extends the of-thermal.c to export copy of trip points
>>>> for a given thermal zone.
>>>>
>>>> Thermal drivers should use of_thermal_get_trip_points() method to
>>>> get pointer to table of thermal trip points.
>>>>
>>>> Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
>>>> ---
>>>> Changes for v2:
>>>> - New patch - as suggested by Eduardo Valentin
>>>> ---
>>>> drivers/thermal/of-thermal.c | 33
>>>> +++++++++++++++++++++++++++++++++ drivers/thermal/thermal_core.h |
>>>> 7 +++++++ include/linux/thermal.h | 14 ++++++++++++++
>>>> 3 files changed, 54 insertions(+)
>>>>
>>>> diff --git a/drivers/thermal/of-thermal.c
>>>> b/drivers/thermal/of-thermal.c index 336af7f..33921c5 100644
>>>> --- a/drivers/thermal/of-thermal.c
>>>> +++ b/drivers/thermal/of-thermal.c
>>>> @@ -89,6 +89,7 @@ struct __thermal_zone {
>>>> /* trip data */
>>>> int ntrips;
>>>> struct __thermal_trip *trips;
>>>> + struct thermal_trip *gtrips;
Do we really need this duplication ?
>>>>
>>>> /* cooling binding data */
>>>> int num_tbps;
>>>> @@ -152,6 +153,27 @@ bool of_thermal_is_trip_en(struct
>>>> thermal_zone_device *tz, int trip) return true;
>>>> }
>>>>
>>>> +/**
>>>> + * of_thermal_get_trip_points - function to get access to a
>>>> globally exported
>>>> + * trip points
>>>> + *
>>>> + * @tz: pointer to a thermal zone
>>>> + *
>>>> + * This function provides a pointer to the copy of trip points
>>>> table
>>>> + *
>>>> + * Return: pointer to trip points table, NULL otherwise
>>>> + */
>>>> +const struct thermal_trip * const
>>>> +of_thermal_get_trip_points(struct thermal_zone_device *tz)
>>>> +{
>>>> + struct __thermal_zone *data = tz->devdata;
>>>> +
>>>> + if (!data)
>>>> + return NULL;
>>>> +
>>>> + return data->gtrips;
>>>> +}
>>>> +
>>>
>>> EXPORT_SYMBOL_GPL(of_thermal_get_trip_points);
>>
>> Ok.
>>
>>>
>>>> static int of_thermal_get_trend(struct thermal_zone_device *tz,
>>>> int trip, enum thermal_trend *trend)
>>>> {
>>>> @@ -767,6 +789,16 @@ thermal_of_build_thermal_zone(struct
>>>> device_node *np) goto free_tbps;
>>>> }
>>>>
>>>> + tz->gtrips = kcalloc(tz->ntrips, sizeof(*tz->gtrips),
>>>> GFP_KERNEL);
>>>> + if (!tz->gtrips) {
>>>> + ret = -ENOMEM;
>>>> + goto free_tbps;
>>>> + }
>>>> +
>>>> + for (i = 0; i < tz->ntrips; i++)
>>>> + memcpy(&(tz->gtrips[i]),
>>>> &(tz->trips[i].temperature),
>>>> + sizeof(*tz->gtrips));
>>>> +
>>>> finish:
>>>> of_node_put(child);
>>>> tz->mode = THERMAL_DEVICE_DISABLED;
>>>> @@ -793,6 +825,7 @@ static inline void of_thermal_free_zone(struct
>>>> __thermal_zone *tz) {
>>>> int i;
>>>>
>>>> + kfree(tz->gtrips);
>>>> for (i = 0; i < tz->num_tbps; i++)
>>>> of_node_put(tz->tbps[i].cooling_device);
>>>> kfree(tz->tbps);
Couldn't find the code that updates *gtrips as a result of set_trip_temp via
sysfs.

>>>> diff --git a/drivers/thermal/thermal_core.h
>>>> b/drivers/thermal/thermal_core.h index 466208c..a9580ca 100644
>>>> --- a/drivers/thermal/thermal_core.h
>>>> +++ b/drivers/thermal/thermal_core.h
>>>> @@ -91,6 +91,8 @@ int of_parse_thermal_zones(void);
>>>> void of_thermal_destroy_zones(void);
>>>> int of_thermal_get_ntrips(struct thermal_zone_device *);
>>>> bool of_thermal_is_trip_en(struct thermal_zone_device *, int);
>>>> +const struct thermal_trip * const
>>>> +of_thermal_get_trip_points(struct thermal_zone_device *);
>>>> #else
>>>> static inline int of_parse_thermal_zones(void) { return 0; }
>>>> static inline void of_thermal_destroy_zones(void) { }
>>>> @@ -102,6 +104,11 @@ static inline bool
>>>> of_thermal_is_trip_en(struct thermal_zone_device *, int) {
>>>
>>> This produces compilation error when CONFIG_THERMAL_OF is not set.
>>> Name the parameters to fix.
>>
>> As all the other cases, I will fix that.
>>
>>>
>>>> return 0;
>>>> }
>>>> +static inline const struct thermal_trip * const
>>>> +of_thermal_get_trip_points(struct thermal_zone_device *)
>>>> +{
>>>> + return NULL;
>>>> +}
>>>> #endif
>>>>
>>>> #endif /* __THERMAL_CORE_H__ */
>>>> diff --git a/include/linux/thermal.h b/include/linux/thermal.h
>>>> index 5bc28a7..88d7249 100644
>>>> --- a/include/linux/thermal.h
>>>> +++ b/include/linux/thermal.h
>>>> @@ -303,6 +303,20 @@ struct thermal_zone_of_device_ops {
>>>> int (*get_trend)(void *, long *);
>>>> };
>>>>
>>>> +/**
>>>> + * struct thermal_trip - Structure representing themal trip points
>>>> exported from
>>>> + * of-thermal
>>>> + *
>>>
>>> The only problem I have with this name is that would look like it is
>>> in use in all thermal framework, which is not really the case. But I
>>> do think having a type here is a good thing. So, not sure :-)
>>
>> It can stay to be struct thermal_trip or we can rename it to
>> struct of_thermal_trip.
>>
>> I'm fine with both names.
>
> Leave it as 'thermal_trip'.
>
>>
>>>
>>>> + * @temperature: trip point temperature
>>>> + * @hysteresis: trip point hysteresis
>>>> + * @type: trip point type
>>>> + */
>>>> +struct thermal_trip {
>>>> + unsigned long int temperature;
>>>> + unsigned long int hysteresis;
>>>> + enum thermal_trip_type type;
>>>> +};
>>>> +
>>>> /* Function declarations */
>>>> #ifdef CONFIG_THERMAL_OF
>>>> struct thermal_zone_device *
>>>> --
>>>> 2.0.0.rc2
>>>>
>>
>>
>>
>> --
>> Best regards,
>>
>> Lukasz Majewski
>>
>> Samsung R&D Institute Poland (SRPOL) | Linux Platform Group
>
> * Unknown Key
> * 0x7DA4E256
>