Date:	Fri, 29 Aug 2014 07:32:59 -0400
From:	"edubezval@...il.com" <edubezval@...il.com>
To:	Wei Ni <wni@...dia.com>
Cc:	khali@...ux-fr.org, linux@...ck-us.net,
	Stephen Warren <swarren@...dotorg.org>,
	lm-sensors@...sensors.org,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 3/4] thermal: add more description for thermal-zones

Hello Wei,

On Thu, Aug 28, 2014 at 11:03 PM, Wei Ni <wni@...dia.com> wrote:
> On 08/28/2014 09:21 PM, Eduardo Valentin wrote:
>> Hello Wei,
>>
>> On Thu, Aug 28, 2014 at 09:50:01AM +0800, Wei Ni wrote:
>>> On 08/27/2014 09:32 PM, Eduardo Valentin wrote:
>>>> Hello Wei,
>>>>
>>>> On Wed, Aug 27, 2014 at 10:54:07AM +0800, Wei Ni wrote:
>>>>> On 08/26/2014 08:12 PM, Eduardo Valentin wrote:
>>>>>> On Tue, Aug 26, 2014 at 10:17:29AM +0800, Wei Ni wrote:
>>>>>>> On 08/25/2014 07:07 PM, Eduardo Valentin wrote:
>>>>>>>> Hello Wei Ni,
>>>>>>>>
>>>>>>>> On Mon, Aug 25, 2014 at 02:29:47PM +0800, Wei Ni wrote:
>>>>>>>>> Add more description for the "polling-delay" property.
>>>>>>>>> Set "trips" and "cooling maps" as optional property, because
>>>>>>>>> if missing these two sub-nodes, the thermal zone device still
>>>>>>>>> work properly.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Wei Ni <wni@...dia.com>
>>>>>>>>> ---
>>>>>>>>>  Documentation/devicetree/bindings/thermal/thermal.txt | 10 ++++++----
>>>>>>>>>  1 file changed, 6 insertions(+), 4 deletions(-)
>>>>>>>>>
>>>>>>>>> diff --git a/Documentation/devicetree/bindings/thermal/thermal.txt b/Documentation/devicetree/bindings/thermal/thermal.txt
>>>>>>>>> index f5db6b7..e3d3ed9 100644
>>>>>>>>> --- a/Documentation/devicetree/bindings/thermal/thermal.txt
>>>>>>>>> +++ b/Documentation/devicetree/bindings/thermal/thermal.txt
>>>>>>>>> @@ -136,8 +136,8 @@ containing trip nodes and one sub-node containing all the zone cooling maps.
>>>>>>>>>
>>>>>>>>>  Required properties:
>>>>>>>>>  - polling-delay:      The maximum number of milliseconds to wait between polls
>>>>>>>>> -  Type: unsigned      when checking this thermal zone.
>>>>>>>>> -  Size: one cell
>>>>>>>>> +  Type: unsigned      when checking this thermal zone. If this value is 0, the
>>>>>>>>> +  Size: one cell      driver will not run polling queue, but just cancel it.
>>>>>>>>>
>>>>>>>>
>>>>>>>> The description above is specific to Linux kernel implementation
>>>>>>>> nomenclature. DT description needs to be OS agnostic.
>>>>>>>>
>>>>>>>>>  - polling-delay-passive: The maximum number of milliseconds to wait
>>>>>>>>>    Type: unsigned      between polls when performing passive cooling.
>>>>>>>>> @@ -148,14 +148,16 @@ Required properties:
>>>>>>>>>    phandles + sensor
>>>>>>>>>    specifier
>>>>>>>>>
>>>>>>>>> +Optional property:
>>>>>>>>>  - trips:              A sub-node which is a container of only trip point nodes
>>>>>>>>>    Type: sub-node      required to describe the thermal zone.
>>>>>>>>>
>>>>>>>>>  - cooling-maps:               A sub-node which is a container of only cooling device
>>>>>>>>>    Type: sub-node      map nodes, used to describe the relation between trips
>>>>>>>>> -                      and cooling devices.
>>>>>>>>> +                      and cooling devices. If missing the "trips" property,
>>>>>>>>> +                      This sub-node will not be parsed, because no trips can
>>>>>>>>> +                      be bound to cooling devices.
>>>>>>>>
>>>>>>>> Do you mean if the thermal zone misses the "trips" property? Actually,
>>>>>>>> the binding describes both, cooling-maps and trips, as required
>>>>>>>> properties. Thus, both needs to be in place to consider the thermal zone
>>>>>>>> as a proper described zone.
>>>>>>>
>>>>>>> I moved the "trips" and "cooling-maps" to optional property, because if
>>>>>>> missing these two properties, the thermal zone devices still can be
>>>>>>> registered, and the driver can work properly, it has the basic function,
>>>>>>> can read temperature from thermal sysfs, although it doesn't have trips
>>>>>>> and bind with cooling devices.
>>>>>>
>>>>>>
>>>>>> If a thermal zone is used only for monitoring, then I believe it lost
>>>>>> its purpose. As  Maybe a different framework shall be used, such as hwmon,
>>>>>> for instance?
>>>>>
>>>>> Yes, if we only use it for monitoring, we can use hwmon. But we have
>>>>> more functions base on these two thermal zone devices. We have a
>>>>> skin-temperature driver, which used nct1008's remote and local
>>>>> temperatures to estimator the skin temperature. As you know the thermal
>>>>> framework is more powerful, the remote/local sensors can be register as
>>>>> thermal zone, then the skin-temp driver can use thermal_zone_get_temp()
>>>>> to read their temperatures and then estimator skin's temp. We also will
>>>>> set trips and cooling devices for this skin-temp.
>>>>
>>>> In this case, don't you think it would make sense to create a thermal
>>>> zone for the skin temperature and add the required sensors (including
>>>> the nct1008) in it?
>>>
>>> Hi, Eduardo
>>> Yes, we will create a thermal zone for the skin-temp driver and add the
>>> required sensors in it, but in here we want to register these required
>>> sensors as thermal zone devices, then the thermal framework can export
>>> functions to read these sensors temperature. If use hwmon framework, it
>>> can't export nct1008's internal sensors, such as remote/local sensors,
>>> and no exported functions to read these temperatures. If we doesn't use
>>> the thermal/of-thermal framework, we have to develop a new framework to
>>> parse those sensor nodes, and I think this new one may only have slight
>>> difference with current thermal framework.
>>> If we set those two properties as optional property, then we can use it
>>> in this case simply.
>>>
>>> The skin-temp nodes will something like this:
>>>
>>> skin_temp: therm-est {
>>>      compatible = "nvidia,tegra124-therm-est";
>>>
>>>      #thermal-sensor-cells = <0>;
>>>
>>>      sub-devs {
>>>              dev@0 {
>>> /* we need to register nct1008_remote as thermal zone devices, so that
>>> it's easy to handle it by using thermal framework's exported functions. */
>>>                      dev = <&nct1008_remote>;
>>>              };
>>>              dev@1 {
>>>                      dev = <&nct1008_local>;
>>>              };
>>>      };
>>> };
>>>
>>> thermal-zones {
>>>      skin-therm {
>>>              polling-delay-passive = <15000>
>>>              polling-delay = <0>;
>>>
>>>              thermal-sensors = <&skin_temp>;
>>
>> The binding allows you to add several sensors in one thermal zone.
>> Please have a look on the example (c) of the thermal.txt binding
>> description. It might be that what you want to do is actually:
>>               thermal-sensors = <&ntc1008_local>,
>>                               <&ntc1008_remote>;
>
>
> Yes, we have considered it, but in current kernel, it only supports 1
> sensor per zone. and according to the example (c), it's supposed to only
> support simple algorithm, such as:
> /* hotspot = 100 * bandgap - 120 * adc + 484 */
>  coefficients =          <100    -120    484>;
>
> but in our skin-temp driver, we will recored 20 history temperatures for
> every sensors, and set different coefficients for every history
> temperatures, our HW team have private mathematical mode to calculate
> these coeffs for different boards. And I think other users may use
> different algorithm to calculate thermal zone temperature based on
> several sensors.
>
> So I think it's better to register sensors to thermal zones, not set
> trips and binding cooling devices, then user's thermal driver can use
> them freely.
>

In your system, the used governor is userspace, then?

> Thanks.
> Wei.
>
>>
>>
>>>
>>>              trips {
>>>              };
>>>              cooling-maps {
>>>              };
>>>      };
>>> };
>>>
>>> Wei.
>>>>
>>>>>
>>>>> Wei.
>>>>>
>>>>>>
>>>>>> The purpose of a thermal zone is to describe thermal behavior of a
>>>>>> hardware. As it is mentioned in the thermal.txt file.
>>>>>>
>>>>>>
>>>>>>>
>>>>>>> Thanks.
>>>>>>> Wei.
>>>>>>>
>>>>>>>>
>>>>>>>>>
>>>>>>>>> -Optional property:
>>>>>>>>>  - coefficients:               An array of integers (one signed cell) containing
>>>>>>>>>    Type: array         coefficients to compose a linear relation between
>>>>>>>>>    Elem size: one cell the sensors listed in the thermal-sensors property.
>>>>>>>>> --
>>>>>>>>> 1.8.1.5
>>>>>>>>>
>>>>>>>
>>>>>> --
>>>>>> To unsubscribe from this list: send the line "unsubscribe linux-tegra" in
>>>>>> the body of a message to majordomo@...r.kernel.org
>>>>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>>>>
>>>>>
>>>
>



-- 
Eduardo Bezerra Valentin
--
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