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

Guenter Roeck
2014-11-26T21:12:53Z

On 11/26/2014 12:43 PM, navneet kumar wrote:
>
> 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.
>

Sorry, lost you here. What replicated calculation do you refer to ?

Thanks,
Guenter

> 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
>>
>