Re: [PATCH 2/5] dt-bindings: iio: adc: lpc32xx-adc: Document vref-supply

From: Gregory CLEMENT <gregory.clement@bootlin.com>
To: Vladimir Zapolskiy <vz@mleia.com>,
	Jonathan Cameron <jic23@kernel.org>,
	Hartmut Knaack <knaack.h@gmx.de>,
	Lars-Peter Clausen <lars@metafoo.de>,
	Peter Meerwald-Stadler <pmeerw@pmeerw.net>
Cc: devicetree@vger.kernel.org, Rob Herring <robh+dt@kernel.org>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 2/5] dt-bindings: iio: adc: lpc32xx-adc: Document vref-supply
Date: Fri, 15 Feb 2019 17:07:19 +0100	[thread overview]
Message-ID: <87o97d2fyg.fsf@FE-laptop> (raw)
In-Reply-To: <8bc7bfcf-ad04-0615-1735-c2bbf20b7861@mleia.com>

Hi Vladimir,

 On sam., févr. 09 2019, Vladimir Zapolskiy <vz@mleia.com> wrote:

> Hi Gregory,
>
> On 02/08/2019 06:09 PM, Gregory CLEMENT wrote:
>> As most of the other ADC the lpc32xx one use a vref-supply property:
>> document it.
>> 
>> Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
>> ---
>>  Documentation/devicetree/bindings/iio/adc/lpc32xx-adc.txt | 5 +++++
>>  1 file changed, 5 insertions(+)
>> 
>> diff --git a/Documentation/devicetree/bindings/iio/adc/lpc32xx-adc.txt b/Documentation/devicetree/bindings/iio/adc/lpc32xx-adc.txt
>> index b3629d3a9adf..3a1bc669bd51 100644
>> --- a/Documentation/devicetree/bindings/iio/adc/lpc32xx-adc.txt
>> +++ b/Documentation/devicetree/bindings/iio/adc/lpc32xx-adc.txt
>> @@ -6,6 +6,10 @@ Required properties:
>>    region.
>>  - interrupts: The ADC interrupt
>>  
>> +Optional:
>> + - vref-supply: The regulator supply ADC reference voltage, optional
>> +   for legacy reason, but highly encouraging to us in new device tree
>> +
>
> here vref-supply voltage is 3.3v only, I think that might be a reason why
> the property is omitted.

VDD_AD is an external pin so in theroy it would be possible to use a
different voltage, but indeed the datasheet describe this pin as the
3.3V supply for ADC.

>
> My concern is that the documentation shall not contain sections with
> description of properties found in the past for 'legacy reasons', if you
> like to support the backward compatibility in the driver, please update
> the documentation to the expected state and add a stub to care about
> legacy DTBs in the driver only.

I saw a lot of reference about legacy properties in the binding, and I
found it quite usefull when I read old device trees.

>
> FWIW I personally don't mind about breaking the backward compatibility
> for NXP LPC32xx, it might be a concern when CONFIG_ARM_ATAG_DTB_COMPAT=y
> is removed from the lpc32xx_defconfig though.
>
>>  Example:
>>  
>>  	adc@40048000 {
>> @@ -13,4 +17,5 @@ Example:
>>  		reg = <0x40048000 0x1000>;
>>  		interrupt-parent = <&mic>;
>>  		interrupts = <39 0>;
>> +		vref-supply = <&vcc>;
>>  	};
>> 
>
> I kindly ask you to include me to To: list, if you send another changes for
> NXP LPC32xx platform.

Yes sure! I wrongly only use the first lines provided by
./scripts/get_maintainer.pl, I will include you in the next version.

Thanks,

Gregory

>
> Thank you.
>
> --
> Best wishes,
> Vladimir
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

-- 
Gregory Clement, Bootlin
Embedded Linux and Kernel engineering
http://bootlin.com

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