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>
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.../devicetree/bindings/iio/adc/qcom,spmi-vadc.txt | 130 ++++++++++++++++++++
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+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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