From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751266AbcDFQBd (ORCPT ); Wed, 6 Apr 2016 12:01:33 -0400 Received: from mail-pf0-f171.google.com ([209.85.192.171]:32894 "EHLO mail-pf0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750943AbcDFQBb (ORCPT ); Wed, 6 Apr 2016 12:01:31 -0400 Date: Wed, 6 Apr 2016 09:01:27 -0700 From: Eduardo Valentin To: Laxman Dewangan Cc: rui.zhang@intel.com, robh+dt@kernel.org, mark.rutland@arm.com, pawel.moll@arm.com, ijc+devicetree@hellion.org.uk, linux-pm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] thermal: generic-adc: Add DT binding for ADC based thermal sensor driver Message-ID: <20160406160126.GA638@localhost.localdomain> References: <1459936986-2839-1-git-send-email-ldewangan@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1459936986-2839-1-git-send-email-ldewangan@nvidia.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 06, 2016 at 03:33:05PM +0530, Laxman Dewangan wrote: > Sometimes, thermal sensors like NCT thermistors are connected to > the ADC channel. The temperature is read by reading the voltage > across the sensor resistance via ADC and referring the lookup > table for ADC value to temperature. The ADC interface is provided > through the IIO framework. > > Add DT binding doc for the adc based thermal sensor driver to detail > the DT property and provide the example for how to use it. > > Signed-off-by: Laxman Dewangan > --- > .../bindings/thermal/thermal-generic-adc.txt | 86 ++++++++++++++++++++++ > 1 file changed, 86 insertions(+) > create mode 100644 Documentation/devicetree/bindings/thermal/thermal-generic-adc.txt > > diff --git a/Documentation/devicetree/bindings/thermal/thermal-generic-adc.txt b/Documentation/devicetree/bindings/thermal/thermal-generic-adc.txt > new file mode 100644 > index 0000000..6b3e715 > --- /dev/null > +++ b/Documentation/devicetree/bindings/thermal/thermal-generic-adc.txt > @@ -0,0 +1,86 @@ > +General Purpose Analog To Digital Converter (ADC) based thermal sensor > + > +On some of platforms, thermal sensor like thermistors are connected to > +one of ADC channel and sensor resistance is read via voltage across the > +sensor. The voltage read across the sensor is mapped to temperature using > +voltage-temperature lookup table. > + > +This driver provides the interface to sensor-ADC interconnection and > +the relation ship between ADC read value and temperature. > + > +Required properties: > +=================== > +- compatible: Must be "generic-adc-thermal". > +- lower-temperature: Lower temperature for the lookup table > + in millicelsius. > +- upper-temperature: Upper temperature for the lookup table > + in millicelsius. > +- step-temperature: The temperature steps for the reading ADC > + value in millicelsius. How about when you have a sensor that does not have a nice linear stepping correlation ? > +- temperature-lookup-table: The ADC reading value on each step of the > + temperature starting from lower temperature > + to upper temperature. > + When ADC is read, the value is looked up on the > + table to get the equivalent temperature. I would say, we would need to support a two dimensional table here.. > +- #thermal-sensor-cells: Should be 1. See ./thermal.txt for a description > + of this property. > + > +Example : > +#include > + > +i2c@7000c400 { > + ads1015: ads1015@4a { > + reg = <0x4a>; > + compatible = "ads1015"; > + sampling-frequency = <3300>; > + #io-channel-cells = <1>; > + }; > +}; > + > +thermal-sensor@1 { > + compatible = "generic-adc-thermal"; > + #thermal-sensor-cells = <0>; > + io-channels = <&ads1015 1>; > + io-channel-names = "sensor-channel"; > + lower-temperature = <(-40000)>; > + upper-temperature = <125000>; > + step-temperature = <1000>; > + temperature-lookup-table = <2578 2577 2576 2575 2574 > + 2573 2572 2571 2569 2568 > + 2567 2565 2563 2561 2559 > + :::::::::: > + 254 247 240 233 226 220 > + 214 208>; > +}; > + > +dummy_cool_dev: dummy-cool-dev { > + compatible = "dummy-cooling-dev"; > + #cooling-cells = <2>; /* min followed by max */ > +}; > + > +thermal-zones { > + Tboard { > + polling-delay = <15000>; /* milliseconds */ > + polling-delay-passive = <0>; /* milliseconds */ > + thermal-sensors = <&tboard_thermistor>; > + > + trips { > + therm_est_trip: therm_est_trip { > + temperature = <40000>; > + type = "active"; > + hysteresis = <1000>; > + writable; Not sure about writable property, where is it described? > + }; > + }; > + > + cooling-maps { > + map0 { > + trip = <&therm_est_trip>; > + cooling-device = <&dummy_cool_dev THERMAL_NO_LIMIT THERMAL_NO_LIMIT>; > + contribution = <100>; > + cdev-type = "therm_est_activ"; Not sure about cdev-type property, where is it described? > + }; > + }; > + > + }; > +}; > -- > 2.1.4 >