linux-kernel - Re: [PATCH 1/2] dt-bindings: iio: stm32-adc: add option to set resolution

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Message-ID: <b9f59559-c7a8-f575-0868-bd3b149a35c9@st.com>
Date:   Fri, 24 Feb 2017 17:04:45 +0100
From:   Fabrice Gasnier <fabrice.gasnier@...com>
To:     Jonathan Cameron <jic23@...nel.org>, <linux@...linux.org.uk>,
        <robh+dt@...nel.org>, <linux-arm-kernel@...ts.infradead.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     <linux-iio@...r.kernel.org>, <mark.rutland@....com>,
        <mcoquelin.stm32@...il.com>, <alexandre.torgue@...com>,
        <lars@...afoo.de>, <knaack.h@....de>, <pmeerw@...erw.net>
Subject: Re: [PATCH 1/2] dt-bindings: iio: stm32-adc: add option to set
 resolution

On 02/19/2017 01:09 PM, Jonathan Cameron wrote:
> On 15/02/17 16:55, Fabrice Gasnier wrote:
>> Add documentation for 'st,adc-res' dt optional property.
>>
>> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@...com>
> I'm happy with this, but would like to leave time for a device tree review.
>
> Ultimately we may well want to make this a generic property and call it something
> like adc-resolution but perhaps we need to wait until we have a few more devices
> supporting setting it via device tree to figure out what the best interface is.
> It would exactly be a problem to support this as a deprecated binding at that
> point.

Hi Jonathan,

I agree with you on this... It may be better to have generic property
for this, especially if you see that it will come in the near future.
May I suggest this prop to be less restrictive, e.g. like 
resolution-bits as is may also be worth for other device types, e.g. DAC 
as an example ?

>
> Give me a poke if we hear nothing from Rob or Mark for say another week.

No news yet, but it can wait a little longer.

Please advise,
Regards,
Fabrice

>
> Thanks,
>
> Jonathan
>
>> ---
>>  Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt b/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
>> index 5dfc88e..45f7ff2 100644
>> --- a/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
>> +++ b/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
>> @@ -57,6 +57,9 @@ Optional properties:
>>  - dmas: Phandle to dma channel for this ADC instance.
>>    See ../../dma/dma.txt for details.
>>  - dma-names: Must be "rx" when dmas property is being used.
>> +- st,adc-res: Resolution (bits) to use for conversions. Must match device
>> +  available resolutions (e.g. can be 6, 8, 10 or 12 on stm32f4). Default
>> +  is maximum resolution if unset.
>>
>>  Example:
>>  	adc: adc@...12000 {
>> @@ -84,6 +87,7 @@ Example:
>>  			st,adc-channels = <8>;
>>  			dmas = <&dma2 0 0 0x400 0x0>;
>>  			dma-names = "rx";
>> +			st,adc-res = <8>;
>>  		};
>>  		...
>>  		other adc child nodes follow...
>>
>