linux-kernel - Re: [lm-sensors] [RESEND PATCH V1 0/9] thermal: introduce DT thermal zone build

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Date:	Fri, 19 Jul 2013 09:03:43 -0400
From:	Eduardo Valentin <eduardo.valentin@...com>
To:	Guenter Roeck <linux@...ck-us.net>
CC:	Stephen Warren <swarren@...dotorg.org>,
	Eduardo Valentin <eduardo.valentin@...com>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <rob.herring@...xeda.com>,
	<devicetree-discuss@...ts.ozlabs.org>, <wni@...dia.com>,
	<linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<lm-sensors@...sensors.org>, <l.stach@...gutronix.de>
Subject: Re: [lm-sensors] [RESEND PATCH V1 0/9] thermal: introduce DT thermal
 zone build

On 18-07-2013 17:21, Guenter Roeck wrote:
> On Thu, Jul 18, 2013 at 11:18:05AM -0600, Stephen Warren wrote:
>> On 07/18/2013 07:53 AM, Eduardo Valentin wrote:
>>> Hello Guenter,
>>>
>>> On 17-07-2013 18:09, Guenter Roeck wrote:
>>>> On Wed, Jul 17, 2013 at 11:17:19AM -0400, Eduardo Valentin
>>>> wrote:
>>>>> Hello all,
>>>>>
>>>>> As you noticed, I am working in a way to represent thermal
>>>>> data using device tree [1]. Essentially, this should be a way
>>>>> to say what to do with a sensor and how to associate (cooling)
>>>>> actions with it.
>>>>>
>>>> Seems to me that goes way beyond the supposed scope of devicetree
>>>> data. Devicetree data is supposed to describe hardware, not its
>>>> configuration or use. This is clearly a use case.
>>>
>>> Thanks for rising your voice here. It is important to know what
>>> hwmon ppl think about this.
>>
>> I meant to find time to read Guenter's original email where he
>> initially objected to putting data into DT, and determine exactly what
>> was being objected to. I still haven't:-( However, the arguments that
>> Eduardo stated in his email do make sense to me; I agree that
>> temperature limits really are a description of HW. Details of which
>> cooling methods to invoke when certain temperature limits are reached
>> is also part of the HW/system design, and hence I would tend to agree
>> that they're appropriate to include in DT. Anyway, that's just my 2
>> cents on the matter:-)
> 
> Many systems have multiple profiles for various use cases (high performance,
> low power etc), and limits are different based on the use case. If that means
> you are going to have multiple devicetree variants based on the profile,

No, definitely this patch series is *not* about mapping multiples
profiles for various use cases on device tree! This series is about
mapping *hw thermal limits* on device tree.

> I would argue that you crossed the line. With thermal profiles it gets even more
> complicated, as those parameters may be played around with and changed
> multiple times to find the best settings to achieve optimal cooling.
> Does this describe hardware ? I don't think so, but, as I mentioned before,
> maybe I am wrong.


Again, this is about describing points and actions to avoid your hw
degradation. May be also useful to avoid end user harm.

This series is not about describing performance profiles.

> 
> Guenter
> 
> 


-- 
You have got to be excited about what you are doing. (L. Lamport)

Eduardo Valentin


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