iio: hx711: add clock-frequency property in DT

Add clock-frequency property for hx711 ADC. This is the frequency of
PD_SCK.

After PD_SCK goes high DOUT is read just before PD_SCK goes down again.
This is necessary because of parasitic capacitance on the wiring.

Signed-off-by: Andreas Klinger <ak@it-klinger.de>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/Documentation/devicetree/bindings/iio/adc/avia-hx711.txt b/Documentation/devicetree/bindings/iio/adc/avia-hx711.txt
index b3629405f5684ff82ce11a5b0691370030719dc3..2c1b67d33c49a8a953f55a8af66c923cf8a6bf68 100644 (file)
--- a/Documentation/devicetree/bindings/iio/adc/avia-hx711.txt
+++ b/Documentation/devicetree/bindings/iio/adc/avia-hx711.txt
@@ -8,11 +8,17 @@ Required properties:
                See Documentation/devicetree/bindings/gpio/gpio.txt
  - avdd-supply:        Definition of the regulator used as analog supply
 
+Optional properties:
+ - clock-frequency:    Frequency of PD_SCK in Hz
+                       Minimum value allowed is 10 kHz because of maximum
+                       high time of 50 microseconds.
+
 Example:
 weight@0 {
        compatible = "avia,hx711";
        sck-gpios = <&gpio3 10 GPIO_ACTIVE_HIGH>;
        dout-gpios = <&gpio0 7 GPIO_ACTIVE_HIGH>;
        avdd-suppy = <&avdd>;
+       clock-frequency = <100000>;
 };