linux-kernel - Re: [PATCH 0/3] Thermal reset support in PMC

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Date:	Wed, 13 Aug 2014 13:59:00 +0300
From:	Mikko Perttunen <mperttunen@...dia.com>
To:	Thierry Reding <thierry.reding@...il.com>
CC:	"swarren@...dotorg.org" <swarren@...dotorg.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH 0/3] Thermal reset support in PMC



On 13/08/14 13:53, Thierry Reding wrote:
> * PGP Signed by an unknown key
>
> On Wed, Aug 13, 2014 at 01:41:52PM +0300, Mikko Perttunen wrote:
>>
>>
>> On 13/08/14 13:36, Thierry Reding wrote:
>>>> Old Signed by an unknown key
>>>
>>> On Wed, Aug 13, 2014 at 12:52:22PM +0300, Mikko Perttunen wrote:
>>>> On 13/08/14 11:57, Thierry Reding wrote:
>>>>>> Old Signed by an unknown key
>>>>>
>>>>> On Wed, Aug 13, 2014 at 11:42:53AM +0300, Mikko Perttunen wrote:
>>>>>>
>>>>>>
>>>>>> On 13/08/14 11:12, Mikko Perttunen wrote:
>>>>>>> On 13/08/14 11:07, Thierry Reding wrote:
>>>>>>>>> Old Signed by an unknown key
>>>>>>>>
>>>>>>>> On Tue, Aug 05, 2014 at 11:12:57AM +0300, Mikko Perttunen wrote:
>>>>>>>>> Hi,
>>>>>>>>>
>>>>>>>>> this series adds support for hardware-triggered thermal reset to the PMC
>>>>>>>>> driver. Namely, it adds device tree properties for specifying the I2C
>>>>>>>>> command to be sent when thermtrip is triggered. It is to be noted
>>>>>>>>> that thermtrip won't be ever triggered without a soctherm driver to
>>>>>>>>> calibrate the sensors, but I'll follow up with that patch.
>>>>>>>>>
>>>>>>>>> pmc.c required some juggling around to make the match data usable in
>>>>>>>>> probe, since I didn't want to put the code into the initcall either, since
>>>>>>>>> the soctherm driver won't be initialized by that point anyway.
>>>>>>>>>
>>>>>>>>> Series tested on Jetson-TK1. Should work on Tegra30 and Tegra114 too.
>>>>>>>>
>>>>>>>> Can you describe the procedure used to test this? We currently have a
>>>>>>>> bunch of features in Tegra that some people have tested at some point
>>>>>>>> during development but the test procedures never got documented. That
>>>>>>>> means whenever we want to test something we need to go and reinvent a
>>>>>>>> bunch of tests after the fact.
>>>>>>>>
>>>>>>>> So what I'd like to start doing is collect tests (preferably in some
>>>>>>>> scripted way) so that they can be kept in a repository that people can
>>>>>>>> easily clone and run on devices.
>>>>>>>>
>>>>>>>> Could you provide something like that for thermtrip?
>>>>>>>
>>>>>>> Sure. I'll see if I can make a just a test script or if a local patch is
>>>>>>> needed to test. Btw, I also have a pretty nice test script for EMC
>>>>>>> ready, and I agree that such a repository would be very nice.
>>>>>>
>>>>>> Here is a test program. It it works, the device with immediately shut down.
>>>>>>
>>>>>> https://gist.github.com/cyndis/66126c9c176b5f94a76f
>>>>>
>>>>> Is there a way to set the trip temperature without going through
>>>>> /dev/mem? I'd expect the device to have a sysfs interface of some
>>>>> sort.
>>>>
>>>> The thermtrip "device" isn't currently exposed in any way. If it were
>>>> exposed, I suppose it would be exposed as thermal zone devices, each with
>>>> one trip point. Even then, the thermal framework doesn't really support this
>>>> properly; none of the trip point types really apply to this kind of trip
>>>> point, and x86 systems don't expose their trips either.
>>>
>>> Okay. The reason why I asked is because I'm not sure yet that having C
>>> programs in the test suite would be good, so having something that's
>>> easily scriptable would be preferred.
>>
>> I agree. Looks like Python's stdlib has mmap support, so maybe we could use
>> that.
>
> Yes, possibly. It still means that somebody needs to have some kind of
> advanced scripting available to test this. While having a testsuite is
> useful, it would still be nice to occasionally be able to test things
> with just simple shell commands.
>
>>>> Anyway, since debugging is pretty much the only use case for modifying
>>>> the trip temperature, I thought adding the tz_devices would be a bit
>>>> overkill.
>>>
>>> An alternative could be a file in debugfs.
>>
>> True, though there's the "don't expose dangerous stuff in debugfs" argument
>> against that. I don't really have problem with it, though.
>> Although in this case I think the script approach would be good enough.
>
> I've said this before and I don't think "dangerous stuff in debugfs" is
> a valid argument. You need superuser privileges to access debugfs, and
> if you have such privileges you can do pretty much what you want (run
> the test program you posted for example).

I agree with you completely. I guess I can add a debugfs entry to the 
soctherm driver, probably in a separate patch once the original series 
is in. It is then up to the thermal maintainers whether they agree with 
us or not.

>
> Thierry
>
> * Unknown Key
> * 0x7F3EB3A1
>
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