158 lines
4.4 KiB
Plaintext
Executable file
158 lines
4.4 KiB
Plaintext
Executable file
Qualcomm's PM8xxx voltage XOADC
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The Qualcomm PM8xxx PMICs contain a HK/XO ADC (Housekeeping/Crystal
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oscillator ADC) encompassing PM8018, PM8038, PM8058 and PM8921.
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Required properties:
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- compatible: should be one of:
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"qcom,pm8018-adc"
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"qcom,pm8038-adc"
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"qcom,pm8058-adc"
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"qcom,pm8921-adc"
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- reg: should contain the ADC base address in the PMIC, typically
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0x197.
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- xoadc-ref-supply: should reference a regulator that can supply
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a reference voltage on demand. The reference voltage may vary
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with PMIC variant but is typically something like 2.2 or 1.8V.
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The following required properties are standard for IO channels, see
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iio-bindings.txt for more details, but notice that this particular
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ADC has a special addressing scheme that require two cells for
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identifying each ADC channel:
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- #address-cells: should be set to <2>, the first cell is the
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prescaler (on PM8058) or premux (on PM8921) with two valid bits
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so legal values are 0x00, 0x01 or 0x02. The second cell
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is the main analog mux setting (0x00..0x0f). The combination
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of prescaler/premux and analog mux uniquely addresses a hardware
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channel on all systems.
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- #size-cells: should be set to <0>
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- #io-channel-cells: should be set to <2>, again the cells are
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precaler or premux followed by the analog muxing line.
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- interrupts: should refer to the parent PMIC interrupt controller
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and reference the proper ADC interrupt.
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Required subnodes:
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The ADC channels are configured as subnodes of the ADC.
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Since some of them are used for calibrating the ADC, these nodes are
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compulsory:
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adc-channel@c {
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reg = <0x00 0x0c>;
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};
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adc-channel@d {
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reg = <0x00 0x0d>;
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};
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adc-channel@f {
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reg = <0x00 0x0f>;
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};
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These three nodes are used for absolute and ratiometric calibration
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and only need to have these reg values: they are by hardware definition
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1:1 ratio converters that sample 625, 1250 and 0 milliV and create
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an interpolation calibration for all other ADCs.
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Optional subnodes: any channels other than channels [0x00 0x0c],
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[0x00 0x0d] and [0x00 0x0f] are optional.
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Required channel node properties:
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- reg: should contain the hardware channel number in the range
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0 .. 0xff (8 bits).
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Optional channel node properties:
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- qcom,decimation:
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Value type: <u32>
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Definition: This parameter is used to decrease the ADC sampling rate.
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Quicker measurements can be made by reducing the decimation ratio.
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Valid values are 512, 1024, 2048, 4096.
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If the property is not found, a default value of 512 will be used.
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- qcom,ratiometric:
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Value type: <u32>
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Definition: Channel calibration type. If this property is specified
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VADC will use a special voltage references for channel
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calibration. The available references are specified in the
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as a u32 value setting (see below) and it is compulsory
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to also specify this reference if ratiometric calibration
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is selected.
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If the property is not found, the channel will be
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calibrated with the 0.625V and 1.25V reference channels, also
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known as an absolute calibration.
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The reference voltage pairs when using ratiometric calibration:
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0 = XO_IN/XOADC_GND
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1 = PMIC_IN/XOADC_GND
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2 = PMIC_IN/BMS_CSP
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3 (invalid)
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4 = XOADC_GND/XOADC_GND
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5 = XOADC_VREF/XOADC_GND
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Example:
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xoadc: xoadc@197 {
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compatible = "qcom,pm8058-adc";
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reg = <0x197>;
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interrupts-extended = <&pm8058 76 IRQ_TYPE_EDGE_RISING>;
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#address-cells = <2>;
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#size-cells = <0>;
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#io-channel-cells = <2>;
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vcoin: adc-channel@0 {
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reg = <0x00 0x00>;
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};
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vbat: adc-channel@1 {
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reg = <0x00 0x01>;
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};
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dcin: adc-channel@2 {
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reg = <0x00 0x02>;
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};
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ichg: adc-channel@3 {
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reg = <0x00 0x03>;
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};
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vph_pwr: adc-channel@4 {
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reg = <0x00 0x04>;
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};
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usb_vbus: adc-channel@a {
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reg = <0x00 0x0a>;
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};
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die_temp: adc-channel@b {
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reg = <0x00 0x0b>;
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};
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ref_625mv: adc-channel@c {
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reg = <0x00 0x0c>;
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};
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ref_1250mv: adc-channel@d {
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reg = <0x00 0x0d>;
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};
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ref_325mv: adc-channel@e {
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reg = <0x00 0x0e>;
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};
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ref_muxoff: adc-channel@f {
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reg = <0x00 0x0f>;
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};
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};
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/* IIO client node */
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iio-hwmon {
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compatible = "iio-hwmon";
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io-channels = <&xoadc 0x00 0x01>, /* Battery */
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<&xoadc 0x00 0x02>, /* DC in (charger) */
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<&xoadc 0x00 0x04>, /* VPH the main system voltage */
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<&xoadc 0x00 0x0b>, /* Die temperature */
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<&xoadc 0x00 0x0c>, /* Reference voltage 1.25V */
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<&xoadc 0x00 0x0d>, /* Reference voltage 0.625V */
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<&xoadc 0x00 0x0e>; /* Reference voltage 0.325V */
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};
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