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SubjectRe: [PATCH v2 4/7] dt-bindings:iio:resolver: Add docs for ad2s90
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On Sun, 2018-11-18 at 02:25 -0200, Matheus Tavares wrote:
> This patch adds the device tree binding documentation for the ad2s90
> resolver-to-digital converter.
>

One minor comment inline.

> Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
> ---
> Changes in v2:
> - Rewritten 'spi-cpol and spi-cpha' item to say that the device can
> work in either mode (0,0) or (1,1) and explain how they should be
> specified in DT.
>
> .../bindings/iio/resolver/ad2s90.txt | 28 +++++++++++++++++++
> 1 file changed, 28 insertions(+)
> create mode 100644
> Documentation/devicetree/bindings/iio/resolver/ad2s90.txt
>
> diff --git a/Documentation/devicetree/bindings/iio/resolver/ad2s90.txt
> b/Documentation/devicetree/bindings/iio/resolver/ad2s90.txt
> new file mode 100644
> index 000000000000..594417539938
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/resolver/ad2s90.txt
> @@ -0,0 +1,28 @@
> +Analog Devices AD2S90 Resolver-to-Digital Converter
> +
> +https://www.analog.com/en/products/ad2s90.html
> +
> +Required properties:
> + - compatible: should be "adi,ad2s90"
> + - reg: SPI chip select number for the device
> + - spi-max-frequency: set maximum clock frequency, must be 830000
> + - spi-cpol and spi-cpha:
> + Either SPI mode (0,0) or (1,1) must be used, so specify none or
> both of
> + spi-cpha, spi-cpol.
For SPI properties it's a good idea to also reference the document for SPI
bindings.
Something like:
See for more details:
Documentation/devicetree/bindings/spi/spi-bus.txt

> +
> +Note about max frequency:
> + Chip's max frequency, as specified in its datasheet, is 2Mhz. But a
> 600ns
> + delay is expected between the application of a logic LO to CS and
> the
> + application of SCLK, as also specified. And since the delay is not
> + implemented in the spi code, to satisfy it, SCLK's period should be
> at most
> + 2 * 600ns, so the max frequency should be 1 / (2 * 6e-7), which
> gives
> + roughly 830000Hz.
> +
> +Example:
> +resolver@0 {
> + compatible = "adi,ad2s90";
> + reg = <0>;
> + spi-max-frequency = <830000>;
> + spi-cpol;
> + spi-cpha;
> +};
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