174 lines
6.6 KiB
Plaintext
174 lines
6.6 KiB
Plaintext
Qualcomm's SPMI PMIC 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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- SPMI PMIC5 voltage ADC (ADC) provides interface to clients to read
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voltage. The VADC is a 16-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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Should contain "qcom,spmi-adc5" for PMIC5 ADC driver.
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Should contain "qcom,spmi-adc-rev2" for PMIC rev2 ADC driver.
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Should contain "qcom,pms405-adc" for PMS405 PMIC
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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 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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- label:
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Usage: required for "qcom,spmi-adc5" and "qcom,spmi-adc-rev2"
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Value type: <empty>
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Definition: ADC input of the platform as seen in the schematics.
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For thermistor inputs connected to generic AMUX or GPIO inputs
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these can vary across platform for the same pins. Hence select
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the platform schematics name for this channel.
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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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- For compatible property "qcom,spmi-vadc", valid values are
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512, 1024, 2048, 4096. If property is not found, default value
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of 512 will be used.
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- For compatible property "qcom,spmi-adc5", valid values are 250, 420
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and 840. If property is not found, default value of 840 is used.
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- For compatible property "qcom,spmi-adc-rev2", valid values are 256,
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512 and 1024. If property is not present, default value is 1024.
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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.
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- For compatible property "qcom,spmi-vadc", if this property is
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specified VADC will use the VDD reference (1.8V) and GND for
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channel 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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- For compatible property "qcom,spmi-adc5" and "qcom,spmi-adc-rev2",
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if this property is specified VADC will use the VDD reference
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(1.875V) and GND for channel calibration. If property is not found,
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channel will be calibrated with 0V and 1.25V reference channels,
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also 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. The 'hw_settle_time' is an index used from valid values
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and programmed in hardware to achieve the hardware settling delay.
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- For compatible property "qcom,spmi-vadc" and "qcom,spmi-adc-rev2",
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Delay = 100us * (hw_settle_time) for hw_settle_time < 11,
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and 2ms * (hw_settle_time - 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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- For compatible property "qcom,spmi-adc5", delay = 15us for
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value 0, 100us * (value) for values < 11,
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and 2ms * (value - 10) otherwise.
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Valid values are: 15, 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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Certain controller digital versions have valid values of
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15, 100, 200, 300, 400, 500, 600, 700, 1, 2, 4, 8, 16, 32, 64, 128 ms
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If property is not found, channel will use 15us.
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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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- For compatible property "qcom,spmi-vadc", valid values
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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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- For compatible property "qcom,spmi-adc5" and "qcom,spmi-adc-rev2",
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valid values are: 1, 2, 4, 8, 16
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If property is not found, 1 sample will be used.
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NOTE:
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For compatible property "qcom,spmi-vadc" following channels, also known as
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reference point channels, are used for result calibration and their channel
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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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#include <dt-bindings/iio/qcom,spmi-vadc.h>
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#include <linux/irq.h>
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/* ... */
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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>;
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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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adc-chan@VADC_LR_MUX10_USB_ID {
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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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