This patch adds documentation of device tree bindings for the STM32 ADC. It's based on linux-v4.18-rc* dt-bindings, at the time of writing: - Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
Signed-off-by: Fabrice Gasnier fabrice.gasnier@st.com Reviewed-by: Simon Glass sjg@chromium.org ---
Changes in v2: None
doc/device-tree-bindings/adc/st,stm32-adc.txt | 141 ++++++++++++++++++++++++++ 1 file changed, 141 insertions(+) create mode 100644 doc/device-tree-bindings/adc/st,stm32-adc.txt
diff --git a/doc/device-tree-bindings/adc/st,stm32-adc.txt b/doc/device-tree-bindings/adc/st,stm32-adc.txt new file mode 100644 index 0000000..07fb6cd --- /dev/null +++ b/doc/device-tree-bindings/adc/st,stm32-adc.txt @@ -0,0 +1,141 @@ +STMicroelectronics STM32 ADC device + +STM32 ADC is a successive approximation analog-to-digital converter. +It has several multiplexed input channels. Conversions can be performed +in single, continuous, scan or discontinuous mode. Result of the ADC is +stored in a left-aligned or right-aligned 32-bit data register. +Conversions can be launched in software or using hardware triggers. + +The analog watchdog feature allows the application to detect if the input +voltage goes beyond the user-defined, higher or lower thresholds. + +Each STM32 ADC block can have up to 3 ADC instances. + +Each instance supports two contexts to manage conversions, each one has its +own configurable sequence and trigger: +- regular conversion can be done in sequence, running in background +- injected conversions have higher priority, and so have the ability to + interrupt regular conversion sequence (either triggered in SW or HW). + Regular sequence is resumed, in case it has been interrupted. + +Contents of a stm32 adc root node: +----------------------------------- +Required properties: +- compatible: Should be one of: + "st,stm32f4-adc-core" + "st,stm32h7-adc-core" + "st,stm32mp1-adc-core" +- reg: Offset and length of the ADC block register set. +- interrupts: One or more interrupts for ADC block. Some parts like stm32f4 + and stm32h7 share a common ADC interrupt line. stm32mp1 has two separate + interrupt lines, one for each ADC within ADC block. +- clocks: Core can use up to two clocks, depending on part used: + - "adc" clock: for the analog circuitry, common to all ADCs. + It's required on stm32f4. + It's optional on stm32h7. + - "bus" clock: for registers access, common to all ADCs. + It's not present on stm32f4. + It's required on stm32h7. +- clock-names: Must be "adc" and/or "bus" depending on part used. +- interrupt-controller: Identifies the controller node as interrupt-parent +- vref-supply: Phandle to the vref input analog reference voltage. +- #interrupt-cells = <1>; +- #address-cells = <1>; +- #size-cells = <0>; + +Optional properties: +- A pinctrl state named "default" for each ADC channel may be defined to set + inX ADC pins in mode of operation for analog input on external pin. + +Contents of a stm32 adc child node: +----------------------------------- +An ADC block node should contain at least one subnode, representing an +ADC instance available on the machine. + +Required properties: +- compatible: Should be one of: + "st,stm32f4-adc" + "st,stm32h7-adc" + "st,stm32mp1-adc" +- reg: Offset of ADC instance in ADC block (e.g. may be 0x0, 0x100, 0x200). +- clocks: Input clock private to this ADC instance. It's required only on + stm32f4, that has per instance clock input for registers access. +- interrupt-parent: Phandle to the parent interrupt controller. +- interrupts: IRQ Line for the ADC (e.g. may be 0 for adc@0, 1 for adc@100 or + 2 for adc@200). +- st,adc-channels: List of single-ended channels muxed for this ADC. + It can have up to 16 channels on stm32f4 or 20 channels on stm32h7, numbered + from 0 to 15 or 19 (resp. for in0..in15 or in0..in19). +- st,adc-diff-channels: List of differential channels muxed for this ADC. + Depending on part used, some channels can be configured as differential + instead of single-ended (e.g. stm32h7). List here positive and negative + inputs pairs as <vinp vinn>, <vinp vinn>,... vinp and vinn are numbered + from 0 to 19 on stm32h7) + Note: At least one of "st,adc-channels" or "st,adc-diff-channels" is required. + Both properties can be used together. Some channels can be used as + single-ended and some other ones as differential (mixed). But channels + can't be configured both as single-ended and differential (invalid). +- #io-channel-cells = <1>: See the IIO bindings section "IIO consumers" in + Documentation/devicetree/bindings/iio/iio-bindings.txt + +Optional properties: +- dmas: Phandle to dma channel for this ADC instance. + See ../../dma/dma.txt for details. +- dma-names: Must be "rx" when dmas property is being used. +- assigned-resolution-bits: Resolution (bits) to use for conversions. Must + match device available resolutions: + * can be 6, 8, 10 or 12 on stm32f4 + * can be 8, 10, 12, 14 or 16 on stm32h7 + Default is maximum resolution if unset. +- st,min-sample-time-nsecs: Minimum sampling time in nanoseconds. + Depending on hardware (board) e.g. high/low analog input source impedance, + fine tune of ADC sampling time may be recommended. + This can be either one value or an array that matches 'st,adc-channels' list, + to set sample time resp. for all channels, or independently for each channel. + +Example: + adc: adc@40012000 { + compatible = "st,stm32f4-adc-core"; + reg = <0x40012000 0x400>; + interrupts = <18>; + clocks = <&rcc 0 168>; + clock-names = "adc"; + vref-supply = <®_vref>; + interrupt-controller; + pinctrl-names = "default"; + pinctrl-0 = <&adc3_in8_pin>; + + #interrupt-cells = <1>; + #address-cells = <1>; + #size-cells = <0>; + + adc@0 { + compatible = "st,stm32f4-adc"; + #io-channel-cells = <1>; + reg = <0x0>; + clocks = <&rcc 0 168>; + interrupt-parent = <&adc>; + interrupts = <0>; + st,adc-channels = <8>; + dmas = <&dma2 0 0 0x400 0x0>; + dma-names = "rx"; + assigned-resolution-bits = <8>; + }; + ... + other adc child nodes follow... + }; + +Example to setup: +- channel 1 as single-ended +- channels 2 & 3 as differential (with resp. 6 & 7 negative inputs) + + adc: adc@40022000 { + compatible = "st,stm32h7-adc-core"; + ... + adc1: adc@0 { + compatible = "st,stm32h7-adc"; + ... + st,adc-channels = <1>; + st,adc-diff-channels = <2 6>, <3 7>; + }; + };