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Diffstat (limited to 'Documentation/devicetree/bindings/iio/adc/qcom,spmi-vadc.txt')
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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 000000000000..0fb46137f936 --- /dev/null +++ b/Documentation/devicetree/bindings/iio/adc/qcom,spmi-vadc.txt @@ -0,0 +1,129 @@ +Qualcomm's SPMI PMIC voltage ADC + +SPMI PMIC voltage ADC (VADC) provides interface to clients to read +voltage. The VADC is a 15-bit sigma-delta ADC. + +VADC node: + +- compatible: + Usage: required + Value type: <string> + Definition: Should contain "qcom,spmi-vadc". + +- reg: + Usage: required + Value type: <prop-encoded-array> + Definition: VADC base address and length in the SPMI PMIC register map. + +- #address-cells: + Usage: required + Value type: <u32> + Definition: Must be one. Child node 'reg' property should define ADC + channel number. + +- #size-cells: + Usage: required + Value type: <u32> + Definition: Must be zero. + +- #io-channel-cells: + Usage: required + Value type: <u32> + Definition: Must be one. For details about IIO bindings see: + Documentation/devicetree/bindings/iio/iio-bindings.txt + +- interrupts: + Usage: optional + Value type: <prop-encoded-array> + Definition: End of conversion interrupt. + +Channel node properties: + +- reg: + Usage: required + Value type: <u32> + Definition: ADC channel number. + See include/dt-bindings/iio/qcom,spmi-vadc.h + +- qcom,decimation: + Usage: optional + Value type: <u32> + Definition: This parameter is used to decrease ADC sampling rate. + 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 on 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 0.625V and 1.25V reference channels, also + known as absolute calibration. + +- 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. + 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: + +Following channels, also known as reference point channels, are used for +result calibration and their channel configuration nodes should be defined: +VADC_REF_625MV and/or VADC_SPARE1(based on PMIC version) VADC_REF_1250MV, +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"; + }; |