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Date:	Mon, 1 Sep 2014 18:26:04 +0800
From:	Wei Ni <wni@...dia.com>
To:	"edubezval@...il.com" <edubezval@...il.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

On 08/29/2014 07:32 PM, edubezval@...il.com wrote:
> 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?

No, we developed a new governor named as "pid governor", it manages
thermals based on output values of PID controller.

Indeed, our thermal management includes skin-temp, soc-thermal,
cpu-throttle driver and pid governor. This pach set is prepared for the
skin-temp driver.
As you know the tegra soc-therm is in upstreaming, and we will post
other drivers step by step.

Thanks.
Wei.

> 
>> 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
>>>>>>>
>>>>>>
>>>>
>>
> 
> 
> 

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