linux-kernel - Re: [PATCH v2 5/5] ARM: tegra: Add thermal reset (thermtrip) support to PMC

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Date:	Fri, 22 Aug 2014 15:55:56 +0300
From:	Mikko Perttunen <mperttunen@...dia.com>
To:	Stephen Warren <swarren@...dotorg.org>, <thierry.reding@...il.com>
CC:	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-tegra@...r.kernel.org>, <wni@...dia.com>
Subject: Re: [PATCH v2 5/5] ARM: tegra: Add thermal reset (thermtrip) support
 to PMC



On 21/08/14 18:40, Stephen Warren wrote:
> On 08/21/2014 07:11 AM, Mikko Perttunen wrote:
>> On 20/08/14 23:25, Stephen Warren wrote:
>>> On 08/13/2014 06:41 AM, Mikko Perttunen wrote:
>>>> This adds a device tree controlled option to enable PMC-based
>>>> thermal reset in overheating situations. Thermtrip is supported on
>>>> Tegra30, Tegra114 and Tegra124. The thermal reset only works when
>>>> the thermal sensors are calibrated, so a soctherm driver is also
>>>> required.
>>>
>>> If calibration is required, presumably the soctherm must initialize
>>> before this thermtrip code can initialize, or this thermtrip logic might
>>> be triggered by uncalibrated sensors?
>>
>> SOCTHERM requires that each sensor be explicitly enabled before it gives
>> readings. If a sensor is not enabled, the temperature given by the
>> register (and used to trigger thermtrip) will be zero. So in order for a
>> thermtrip shutdown to be caused before soctherm is initialized, the
>> thermtrip temperature would have to be programmed to below zero (the
>> default value is 105C), in which case an immediate shutdown would
>> probably be in order anyway (unless the user uses LN2 or something to
>> cool the soc below zero).
>>
>>>
>>> If so, then there needs to be some explicit mechanism to force the two
>>> drivers into probing in the right order.
>>
>> Because of the above, I think it isn't necessary to probe these in order.
>
> OK, that makes sense. Briefly mentioning this in the commit description
> could be useful.
>

Sure, I'll add a mention to the next version.

Mikko
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