On Tue, Aug 22, 2017 at 03:33:00PM +0200, Lukas Wunner wrote:
> All chips supported by this driver clock data out on the falling edge
> and latch data in on the rising edge, hence SPI mode (0,0) or (1,1)
> must be used.
>
> Furthermore, none of the chips has an internal reference voltage
> regulator, so an external supply is always required and needs to be
> specified in the device tree lest the IIO "scale" in sysfs cannot be
> calculated.
>
> Document these requirements in the device tree binding, together with
> the new "microchip,continuous-conversion" property added specifically
> for the mcp3550/1/3.
>
> Cc: Mathias Duckeck <m.duckeck@xxxxxxxxx>
> Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx>
> ---
> .../devicetree/bindings/iio/adc/mcp320x.txt | 23 ++++++++++++++++++++++
> 1 file changed, 23 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/iio/adc/mcp320x.txt b/Documentation/devicetree/bindings/iio/adc/mcp320x.txt
> index bcd3ac8e6e0c..cf28af9ec0ac 100644
> --- a/Documentation/devicetree/bindings/iio/adc/mcp320x.txt
> +++ b/Documentation/devicetree/bindings/iio/adc/mcp320x.txt
> @@ -29,15 +29,38 @@ Required properties:
> "microchip,mcp3204"
> "microchip,mcp3208"
> "microchip,mcp3301"
> + "microchip,mcp3550-50"
> + "microchip,mcp3550-60"
> + "microchip,mcp3551"
> + "microchip,mcp3553"
>
> NOTE: The use of the compatibles with no vendor prefix
> is deprecated and only listed because old DT use them.
>
> + - spi-cpha, spi-cpol (boolean):
> + Either SPI mode (0,0) or (1,1) must be used, so specify
> + none or both of spi-cpha, spi-cpol. The MCP3550/1/3
> + is more efficient in mode (1,1) as only 3 instead of
> + 4 bytes need to be read from the ADC, but not all SPI
> + masters support it.
> +
> + - vref-supply: Phandle to the external reference voltage supply.
> +
> +Optional properties:
> + - microchip,continuous-conversion (boolean):
Second binding I have seen today with a continuous property. Make this
common (or maybe we already have one).
> + Only applicable to MCP3550/1/3: These ADCs have long
> + conversion times and therefore support "continuous
> + conversion mode" to allow retrieval of conversions
> + at any time without observing a delay. The mode is
> + enabled by permanently driving CS low, e.g. by wiring
> + it to ground.
> +
> Examples:
> spi_controller {
> mcp3x0x@0 {
> compatible = "mcp3002";
> reg = <0>;
> spi-max-frequency = <1000000>;
> + vref-supply = <&vref_reg>;
> };
> };
> --
> 2.11.0
>
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