linux-kernel - Re: [PATCH 2/3] ARM: DTS: Add NTC thermistor nodes to Exynos5250 based Snow

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Date:	Thu, 26 Jun 2014 22:23:40 +0530
From:	Naveen Krishna Ch <naveenkrishna.ch@...il.com>
To:	Doug Anderson <dianders@...omium.org>,
	Kukjin Kim <kgene.kim@...sung.com>
Cc:	Naveen Krishna Chatradhi <ch.naveen@...sung.com>,
	linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	linux-iio <linux-iio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"cpgs ." <cpgs@...sung.com>, Tushar Behera <tushar.b@...sung.com>
Subject: Re: [PATCH 2/3] ARM: DTS: Add NTC thermistor nodes to Exynos5250
 based Snow

Hello Doug and Kukjin,

On 26 June 2014 21:16, Doug Anderson <dianders@...omium.org> wrote:
> Naveen,
>
> On Thu, Jun 26, 2014 at 5:19 AM, Naveen Krishna Chatradhi
> <ch.naveen@...sung.com> wrote:
>> Exynos5250 based Snow board has 4 NTC thermistors to measure
>> temperatures at various points on the board.
>>
>> IIO based ADC becomes the parent and NTC thermistors are the childs,
>> via the HWMON interface.
>>
>> Signed-off-by: Naveen Krishna Chatradhi <ch.naveen@...sung.com>
>> ---
>> Posted earlier by Doug Anderson @ https://lkml.org/lkml/2013/3/27/453
>>
>> This patch depends on (1/4 and 2/4 patches of) patchset posted
>> http://www.spinics.net/lists/linux-iio/msg13486.html
>> Which were applied on to Guenter Roeck's tree.
>>
>> cat sysfs entries exported by hwmon for 4 thermistors
>> and verified the values on Snow.
>>
>>  arch/arm/boot/dts/exynos5250-snow.dts |   34 +++++++++++++++++++++++++++++++++
>>  1 file changed, 34 insertions(+)
>
> NAK.
>
> The first chunk of exynos5250-snow devices have the thermistors
> populated, but a huge chunk of devices also _don't_ have them
> populated.

I've realized only the rev4 and before boards have thermistors
while going through the git logs of snow related dts files
in an older chrome kernel.


>
> If I remember my history properly, rev3 and earlier all had
> thermistors.  Some of rev4 might have thermistors (I never got a clear
> answer).  ...and rev5 definitely doesn't have resistors.  Aside from
> thermistors there's no good reason to differentiate rev3 and rev4
> (they just have different memory).  The upstream kernel may eventually
> need to differentiate rev4 and rev5 since they have a different audio
> codec.

I've found one patch which says, "No thermistors on Rev5 and above boards"
I still thought, we should support few boards out there.

But, i din't knew they were removed completely.

>
> See <https://chromium-review.googlesource.com/#/c/170841/> for some
> descriptions of the different revisions of snow and how they were
> handled in the Chrome OS tree.

Got it now, Thanks

>
> See <https://chromium-review.googlesource.com/#/c/186357/> for
> thermistors talk.  Patch set #1 actually split out rev3, but we then
> decided that we really didn't need to use the thermistors on any of
> the revisions so the later patchsets just totally take them out.

So, no need of thermistor nodes on Snow.
I thought https://lkml.org/lkml/2013/3/27/453 patch is missed out.

>
> -Doug

Kukjin, Sorry for the confusion. Please drop this one.

-- 
Thanks,
(: Nav :)
--
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