130 lines
4 KiB
Plaintext
130 lines
4 KiB
Plaintext
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Qualcomm's SPMI PMIC voltage ADC
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SPMI PMIC voltage ADC (VADC) provides interface to clients to read
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voltage. The VADC is a 15-bit sigma-delta ADC.
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VADC node:
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- compatible:
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Usage: required
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Value type: <string>
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Definition: Should contain "qcom,spmi-vadc".
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- reg:
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Usage: required
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Value type: <prop-encoded-array>
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Definition: VADC base address and length in the SPMI PMIC register map.
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- #address-cells:
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Usage: required
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Value type: <u32>
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Definition: Must be one. Child node 'reg' property should define ADC
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channel number.
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- #size-cells:
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Usage: required
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Value type: <u32>
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Definition: Must be zero.
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- #io-channel-cells:
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Usage: required
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Value type: <u32>
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Definition: Must be one. For details about IIO bindings see:
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Documentation/devicetree/bindings/iio/iio-bindings.txt
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- interrupts:
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Usage: optional
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Value type: <prop-encoded-array>
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Definition: End of conversion interrupt.
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Channel node properties:
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- reg:
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Usage: required
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Value type: <u32>
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Definition: ADC channel number.
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See include/dt-bindings/iio/qcom,spmi-vadc.h
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- qcom,decimation:
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Usage: optional
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Value type: <u32>
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Definition: This parameter is used to decrease ADC sampling rate.
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Quicker measurements can be made by reducing decimation ratio.
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Valid values are 512, 1024, 2048, 4096.
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If property is not found, default value of 512 will be used.
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- qcom,pre-scaling:
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Usage: optional
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Value type: <u32 array>
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Definition: Used for scaling the channel input signal before the signal is
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fed to VADC. The configuration for this node is to know the
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pre-determined ratio and use it for post scaling. Select one from
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the following options.
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<1 1>, <1 3>, <1 4>, <1 6>, <1 20>, <1 8>, <10 81>, <1 10>
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If property is not found default value depending on chip will be used.
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- qcom,ratiometric:
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Usage: optional
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Value type: <empty>
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Definition: Channel calibration type. If this property is specified
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VADC will use the VDD reference (1.8V) and GND for channel
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calibration. If property is not found, channel will be
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calibrated with 0.625V and 1.25V reference channels, also
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known as absolute calibration.
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- qcom,hw-settle-time:
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Usage: optional
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Value type: <u32>
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Definition: Time between AMUX getting configured and the ADC starting
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conversion. Delay = 100us * (value) for value < 11, and
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2ms * (value - 10) otherwise.
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Valid values are: 0, 100, 200, 300, 400, 500, 600, 700, 800,
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900 us and 1, 2, 4, 6, 8, 10 ms
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If property is not found, channel will use 0us.
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- qcom,avg-samples:
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Usage: optional
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Value type: <u32>
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Definition: Number of samples to be used for measurement.
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Averaging provides the option to obtain a single measurement
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from the ADC that is an average of multiple samples. The value
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selected is 2^(value).
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Valid values are: 1, 2, 4, 8, 16, 32, 64, 128, 256, 512
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If property is not found, 1 sample will be used.
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NOTE:
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Following channels, also known as reference point channels, are used for
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result calibration and their channel configuration nodes should be defined:
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VADC_REF_625MV and/or VADC_SPARE1(based on PMIC version) VADC_REF_1250MV,
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VADC_GND_REF and VADC_VDD_VADC.
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Example:
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/* VADC node */
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pmic_vadc: vadc@3100 {
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compatible = "qcom,spmi-vadc";
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reg = <0x3100 0x100>;
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interrupts = <0x0 0x31 0x0 IRQ_TYPE_EDGE_RISING>;
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#address-cells = <1>;
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#size-cells = <0>;
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#io-channel-cells = <1>;
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io-channel-ranges;
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/* Channel node */
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usb_id_nopull {
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reg = <VADC_LR_MUX10_USB_ID>;
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qcom,decimation = <512>;
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qcom,ratiometric;
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qcom,hw-settle-time = <200>;
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qcom,avg-samples = <1>;
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qcom,pre-scaling = <1 3>;
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};
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};
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/* IIO client node */
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usb {
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io-channels = <&pmic_vadc VADC_LR_MUX10_USB_ID>;
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io-channel-names = "vadc";
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};
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