[PATCH v3 2/2] DT: iio: vadc: document dt binding

[Stanimir Varbanov]

Document DT binding for Qualcomm SPMI PMIC voltage ADC
driver.

Signed-off-by: Stanimir Varbanov <svarbanov@xxxxxxxxxx>
Signed-off-by: Ivan T. Ivanov <iivanov@xxxxxxxxxx>
---
 .../devicetree/bindings/iio/adc/qcom,spmi-vadc.txt |  130 ++++++++++++++++++++
 1 files changed, 130 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/qcom,spmi-vadc.txt

diff --git a/Documentation/devicetree/bindings/iio/adc/qcom,spmi-vadc.txt b/Documentation/devicetree/bindings/iio/adc/qcom,spmi-vadc.txt
new file mode 100644
index 0000000..fa30300
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/adc/qcom,spmi-vadc.txt
@@ -0,0 +1,130 @@
+Qualcomm's SPMI PMIC voltage ADC
+
+SPMI PMIC voltage ADC (VADC) provides interface to clients to read
+voltage. A 15 bit ADC is used for voltage measurements. There are multiple
+peripherals to the VADC and the scope of the driver is to provide interface
+for the USR peripheral of the VADC.
+
+VADC node:
+
+- compatible:
+    Usage: required
+    Value type: <string>
+    Definition: Should contain "qcom,spmi-vadc".
+
+- reg:
+    Usage: required
+    Value type: <u32>
+    Definition: Base address in the SPMI PMIC register map.
+
+- address-cells:
+    Usage: required
+    Value type: <u32>
+    Definition: Must be one.
+
+- size-cells:
+    Usage: required
+    Value type: <u32>
+    Definition: Must be zero.
+
+- interrupts:
+    Usage: optional
+    Value type: <prop-encoded-array>
+    Definition: End of conversion interrupt number. If this property does
+            not exist polling will be used instead.
+
+- interrupt-names:
+    Usage: optional
+    Value type: <string>
+    Definition: Should contain the interrupt name "eoc" (end of conversion).
+
+Channel node properties:
+
+- reg:
+    Usage: required
+    Value type: <u32>
+    Definition: AMUX channel number.
+            See include/dt-bindings/iio/qcom,spmi-pmic-vadc.h
+
+- qcom,decimation:
+    Usage: optional
+    Value type: <u32>
+    Definition: Sampling rate to use for the individual channel measurement.
+            Quicker measurements can be made by reducing decimation ratio.
+            Valid values are 512, 1024, 2048, 4096.
+            If property is not found, default value of 512 will be used.
+
+- qcom,pre-scaling:
+    Usage: optional
+    Value type: <u32 array>
+    Definition: Used for scaling the channel input signal before the signal is
+            fed to VADC. The configuration for this node is to know the
+            pre-determined ratio and use it for post scaling. Select one from
+            the following options.
+            <1 1>, <1 3>, <1 4>, <1 6>, <1 20>, <1 8>, <10 81>, <1 10>
+            If property is not found default value depending of chip will be used.
+
+- qcom,ratiometric:
+    Usage: optional
+    Value type: <empty>
+    Definition: Channel calibration type. If this property is specified
+            VADC will use the VDD reference(1.8V) and GND for channel
+            calibration. If property is not found, channel will be
+            calibrated with 625mV and 1.25V reference channels.
+            Otherwise the absolute calibration will be used.
+
+- qcom,hw-settle-time:
+    Usage: optional
+    Value type: <u32>
+    Definition: Time between AMUX getting configured and the ADC starting
+            conversion. Delay = 100us * (value) for value < 11, and
+            2ms * (value - 10) otherwise.
+            Valid values are: 0, 100, 200, 300, 400, 500, 600, 700, 800,
+            900 us and 1, 2, 4, 6, 8, 10 ms
+            If property is not found, channel will use 0us.
+
+- qcom,avg-samples:
+    Usage: optional
+    Value type: <u32>
+    Definition: Number of samples to be used for measurement.
+            Fast averaging provides the option to obtain a single measurement
+            from the ADC that is an average of multiple samples. The value
+            selected is 2^(value).
+            Valid values are: 1, 2, 4, 8, 16, 32, 64, 128, 256, 512
+            If property is not found, 1 sample will be used.
+
+NOTE: At least reference channel nodes are required. The reference channels
+      might be different depending on PMIC version.
+      Reference channels per type of calibration are:
+       - absolute
+         (VADC_REF_625MV or VADC_SPARE1) and VADC_REF_1250MV
+       - ratiomatric
+         VADC_GND_REF and VADC_VDD_VADC
+
+Example:
+	/* VADC node */
+	pmic_vadc: vadc@3100 {
+		compatible = "qcom,spmi-vadc";
+		reg = <0x3100 0x100>;
+		interrupts = <0x0 0x31 0x0 IRQ_TYPE_EDGE_RISING>;
+		#address-cells = <1>;
+		#size-cells = <0>;
+		#io-channel-cells = <1>;
+		io-channel-ranges;
+
+		/* Channel node */
+		usb_id_nopull {
+			reg = <VADC_LR_MUX10_USB_ID>;
+			qcom,decimation = <512>;
+			qcom,ratiometric;
+			qcom,hw-settle-time = <200>;
+			qcom,avg-samples = <1>;
+			qcom,pre-scaling = <1 3>;
+		};
+	};
+
+	/* IIO client node */
+	usb {
+		io-channels = <&pmic_vadc VADC_LR_MUX10_USB_ID>;
+		io-channel-names = "vadc";
+	};
-- 
1.7.0.4

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