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

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Date:	Thu, 21 Aug 2014 09:40:02 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Mikko Perttunen <mperttunen@...dia.com>, 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 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.

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