linux-kernel - Re: [PATCH v2 01/10] dt-bindings: iio: adc: ad7606: Set the correct polarity

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Message-ID: <7mk56pxpgnlu637xo7yypzfdienyh3doch3l3fkinpqbwihf33@nu7v35gdw5zn>
Date: Sat, 21 Sep 2024 11:11:31 +0200
From: Uwe Kleine-König <u.kleine-koenig@...libre.com>
To: Guillaume Stols <gstols@...libre.com>
Cc: Lars-Peter Clausen <lars@...afoo.de>, 
	Michael Hennerich <Michael.Hennerich@...log.com>, Jonathan Cameron <jic23@...nel.org>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Conor Dooley <conor+dt@...nel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	"Rafael J. Wysocki" <rafael@...nel.org>, Jonathan Corbet <corbet@....net>, Michal Marek <mmarek@...e.com>, 
	linux-pwm@...r.kernel.org, linux-kernel@...r.kernel.org, linux-fbdev@...r.kernel.org, 
	linux-iio@...r.kernel.org, devicetree@...r.kernel.org, linux-doc@...r.kernel.org, 
	aardelean@...libre.com, dlechner@...libre.com, jstephan@...libre.com
Subject: Re: [PATCH v2 01/10] dt-bindings: iio: adc: ad7606: Set the correct
 polarity

Hello Guillaume,

On Fri, Sep 20, 2024 at 05:33:21PM +0000, Guillaume Stols wrote:
> According to the datasheet, "Data is clocked in from SDI on the falling
> edge of SCLK, while data is clocked out on DOUTA on the rising edge of
> SCLK".
> Also, even if not stated textually in the datasheet, it is made clear on
> the diagrams that sclk idles at high.
> 
> So the documentation is erroneously stating that spi-cpha is required, and
> the example is erroneously setting both spi-cpol and spi-cpha.

I would expect that the communication with the chip is at least
unreliable if not outright broken with the wrong polarity. So maybe add
something like:

	On $MyMachine dropping the spi-cpha property reduces IO errors / fixes
	measurement readout / improves somehow differently.

to the commit log?

> Fixes: 416f882c3b40 ("dt-bindings: iio: adc: Migrate AD7606 documentation to yaml")
> Fixes: 6e33a125df66 ("dt-bindings: iio: adc: Add docs for AD7606 ADC")
> 
> Signed-off-by: Guillaume Stols <gstols@...libre.com>

The empty line between Fixes and S-o-b is unusual. Assuming you resend
anyway, please drop it.

> diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7606.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7606.yaml
> index 69408cae3db9..75334a033539 100644
> --- a/Documentation/devicetree/bindings/iio/adc/adi,ad7606.yaml
> +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7606.yaml
> @@ -29,8 +29,6 @@ properties:
>    reg:
>      maxItems: 1
>  
> -  spi-cpha: true
> -
>    spi-cpol: true
>  
>    avcc-supply: true
> @@ -117,7 +115,7 @@ properties:
>  required:
>    - compatible
>    - reg
> -  - spi-cpha
> +  - spi-cpol

Adding cpol seems unrelated to this patch. (And you remove it again in
patch #2.)

>    - avcc-supply
>    - vdrive-supply
>    - interrupts

Best regards
Uwe

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