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[PATCH 2/3] dt-bindings: iio: adc: stm32: add optional min-sample-time

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  [PATCH 2/3] dt-bindings: iio: adc: stm32: add optional min-sample-time Fabrice Gasnier <fabrice.gasnier@st.com> - 2017-07-18 14:40 +0200
    Re: [PATCH 2/3] dt-bindings: iio: adc: stm32: add optional  min-sample-time Jonathan Cameron <jic23@kernel.org> - 2017-07-23 13:00 +0200
      Re: [PATCH 2/3] dt-bindings: iio: adc: stm32: add optional  min-sample-time Fabrice Gasnier <fabrice.gasnier@st.com> - 2017-07-24 10:00 +0200
        Re: [PATCH 2/3] dt-bindings: iio: adc: stm32: add optional  min-sample-time Jonathan Cameron <Jonathan.Cameron@huawei.com> - 2017-07-24 17:10 +0200

#1690229 — [PATCH 2/3] dt-bindings: iio: adc: stm32: add optional min-sample-time

STM32 ADC allows each channel to be sampled with a different sampling
time. There's an application note that deals with this: 'How to get
the best ADC accuracy in STM32...' It basically depends on analog input
signal electrical properties (depends on board).

Add optional 'min-sample-time' property so this can be tuned in dt.

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
---
 Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt b/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
index 8310073..9cd964b 100644
--- a/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
+++ b/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
@@ -74,6 +74,11 @@ Optional properties:
   * can be 6, 8, 10 or 12 on stm32f4
   * can be 8, 10, 12, 14 or 16 on stm32h7
   Default is maximum resolution if unset.
+- min-sample-time: Minimum sampling time in nanoseconds.
+  Depending on hardware (board) e.g. high/low analog input source impedance,
+  fine tune of ADC sampling time may be recommended.
+  This can be either one value or an array that matches 'st,adc-channels' list,
+  to set sample time resp. for all channels, or independently for each channel.
 
 Example:
 	adc: adc@40012000 {
-- 
1.9.1

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#1694294 — Re: [PATCH 2/3] dt-bindings: iio: adc: stm32: add optional min-sample-time

On Tue, 18 Jul 2017 14:35:31 +0200
Fabrice Gasnier <fabrice.gasnier@st.com> wrote:

> STM32 ADC allows each channel to be sampled with a different sampling
> time. There's an application note that deals with this: 'How to get
> the best ADC accuracy in STM32...' It basically depends on analog input
> signal electrical properties (depends on board).
> 
> Add optional 'min-sample-time' property so this can be tuned in dt.
> 
> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>

This isn't yet very standard, so I think it needs a manufacturer
prefix, e.g. st,min-sample-time.  Also convention is I believe
to include the units as part of the naming where appropriate.

Hence st,min-sample-time-nsecs

Otherwise, seems good to me.

Jonathan
> ---
>  Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt b/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
> index 8310073..9cd964b 100644
> --- a/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
> +++ b/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
> @@ -74,6 +74,11 @@ Optional properties:
>    * can be 6, 8, 10 or 12 on stm32f4
>    * can be 8, 10, 12, 14 or 16 on stm32h7
>    Default is maximum resolution if unset.
> +- min-sample-time: Minimum sampling time in nanoseconds.
> +  Depending on hardware (board) e.g. high/low analog input source impedance,
> +  fine tune of ADC sampling time may be recommended.
> +  This can be either one value or an array that matches 'st,adc-channels' list,
> +  to set sample time resp. for all channels, or independently for each channel.
>  
>  Example:
>  	adc: adc@40012000 {

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#1694512 — Re: [PATCH 2/3] dt-bindings: iio: adc: stm32: add optional min-sample-time

On 07/23/2017 12:53 PM, Jonathan Cameron wrote:
> On Tue, 18 Jul 2017 14:35:31 +0200
> Fabrice Gasnier <fabrice.gasnier@st.com> wrote:
> 
>> STM32 ADC allows each channel to be sampled with a different sampling
>> time. There's an application note that deals with this: 'How to get
>> the best ADC accuracy in STM32...' It basically depends on analog input
>> signal electrical properties (depends on board).
>>
>> Add optional 'min-sample-time' property so this can be tuned in dt.
>>
>> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
> 
> This isn't yet very standard, so I think it needs a manufacturer
> prefix, e.g. st,min-sample-time.  Also convention is I believe
> to include the units as part of the naming where appropriate.
> 
> Hence st,min-sample-time-nsecs

Hi Jonathan,

I originally used st,... form, when writing this patch, until I found
out there's 'min-sample-time' in vf610 adc dt-bindings:
- Documentation/devicetree/bindings/iio/adc/vf610-adc.txt
It looks like to me very similar.

I also agree it misses '-nsecs' units. Sure, I can use your suggestion
above...

Please can you just confirm if I should use same property as vf610 adc,
or 'st,min-sample-time-nsecs' ?

Thanks for reviewing,
Best regards,
Fabrice

> 
> Otherwise, seems good to me.
> 
> Jonathan
>> ---
>>  Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt | 5 +++++
>>  1 file changed, 5 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt b/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
>> index 8310073..9cd964b 100644
>> --- a/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
>> +++ b/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
>> @@ -74,6 +74,11 @@ Optional properties:
>>    * can be 6, 8, 10 or 12 on stm32f4
>>    * can be 8, 10, 12, 14 or 16 on stm32h7
>>    Default is maximum resolution if unset.
>> +- min-sample-time: Minimum sampling time in nanoseconds.
>> +  Depending on hardware (board) e.g. high/low analog input source impedance,
>> +  fine tune of ADC sampling time may be recommended.
>> +  This can be either one value or an array that matches 'st,adc-channels' list,
>> +  to set sample time resp. for all channels, or independently for each channel.
>>  
>>  Example:
>>  	adc: adc@40012000 {
> 

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#1694798 — Re: [PATCH 2/3] dt-bindings: iio: adc: stm32: add optional min-sample-time

On Mon, 24 Jul 2017 09:55:37 +0200
Fabrice Gasnier <fabrice.gasnier@st.com> wrote:

> On 07/23/2017 12:53 PM, Jonathan Cameron wrote:
> > On Tue, 18 Jul 2017 14:35:31 +0200
> > Fabrice Gasnier <fabrice.gasnier@st.com> wrote:
> >   
> >> STM32 ADC allows each channel to be sampled with a different sampling
> >> time. There's an application note that deals with this: 'How to get
> >> the best ADC accuracy in STM32...' It basically depends on analog input
> >> signal electrical properties (depends on board).
> >>
> >> Add optional 'min-sample-time' property so this can be tuned in dt.
> >>
> >> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>  
> > 
> > This isn't yet very standard, so I think it needs a manufacturer
> > prefix, e.g. st,min-sample-time.  Also convention is I believe
> > to include the units as part of the naming where appropriate.
> > 
> > Hence st,min-sample-time-nsecs  
> 
> Hi Jonathan,
> 
> I originally used st,... form, when writing this patch, until I found
> out there's 'min-sample-time' in vf610 adc dt-bindings:
> - Documentation/devicetree/bindings/iio/adc/vf610-adc.txt
> It looks like to me very similar.
> 
> I also agree it misses '-nsecs' units. Sure, I can use your suggestion
> above...
> 
> Please can you just confirm if I should use same property as vf610 adc,
> or 'st,min-sample-time-nsecs' ?
st,min-sample-time-nsecs.

We might well add a generic option in future, but the burden of
supporting this old one will be trivial anyway so not a problem.

Jonathan
> 
> Thanks for reviewing,
> Best regards,
> Fabrice
> 
> > 
> > Otherwise, seems good to me.
> > 
> > Jonathan  
> >> ---
> >>  Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt | 5 +++++
> >>  1 file changed, 5 insertions(+)
> >>
> >> diff --git a/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt b/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
> >> index 8310073..9cd964b 100644
> >> --- a/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
> >> +++ b/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
> >> @@ -74,6 +74,11 @@ Optional properties:
> >>    * can be 6, 8, 10 or 12 on stm32f4
> >>    * can be 8, 10, 12, 14 or 16 on stm32h7
> >>    Default is maximum resolution if unset.
> >> +- min-sample-time: Minimum sampling time in nanoseconds.
> >> +  Depending on hardware (board) e.g. high/low analog input source impedance,
> >> +  fine tune of ADC sampling time may be recommended.
> >> +  This can be either one value or an array that matches 'st,adc-channels' list,
> >> +  to set sample time resp. for all channels, or independently for each channel.
> >>  
> >>  Example:
> >>  	adc: adc@40012000 {  
> >   
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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