Re: [PATCH v3 3/4] thermal: add more description for thermal-zones

[Wei Ni]

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@xxxxxxxxxx>
>>>>>>>> ---
>>>>>>>>  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.

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
>>>>>>>>
>>>>>>
>>>>> --
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>>>>>
>>>>
>>

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