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@xxxxxx> > --- > 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; > +};
