linux-kernel - Re: [PATCH 01/10] Documentation: dt-bindings: Document STM32 ADC DT bindings

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Message-ID: <20161031030222.vjxcxklpaua3o77d@rob-hp-laptop>
Date:   Sun, 30 Oct 2016 22:02:22 -0500
From:   Rob Herring <robh@...nel.org>
To:     Fabrice Gasnier <fabrice.gasnier@...com>
Cc:     linux-iio@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        jic23@...nel.org, linux@...linux.org.uk, mark.rutland@....com,
        mcoquelin.stm32@...il.com, alexandre.torgue@...com,
        lars@...afoo.de, knaack.h@....de, pmeerw@...erw.net
Subject: Re: [PATCH 01/10] Documentation: dt-bindings: Document STM32 ADC DT
 bindings

On Tue, Oct 25, 2016 at 06:25:13PM +0200, Fabrice Gasnier wrote:
> This patch adds documentation of device tree bindings for the STM32 ADC.
> 
> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@...com>
> ---
>  .../devicetree/bindings/iio/adc/st,stm32-adc.txt   | 78 ++++++++++++++++++++++
>  1 file changed, 78 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt b/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
> new file mode 100644
> index 0000000..a9a8b3c
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
> @@ -0,0 +1,78 @@
> +STMicroelectronics STM32 ADC device driver
> +
> +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.
> +
> +Required properties:
> +- compatible: Should be "st,stm32f4-adc".
> +- reg: Offset and length of the ADC block register set.
> +- interrupts: Must contain the interrupt for ADC.
> +- clocks: Clock for the analog circuitry (common to all ADCs).
> +- clock-names: Must be "adc".
> +- vref-supply: Phandle to the vref input analog reference voltage.
> +- #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.
> +- gpios: Array of gpios that may be configured as EXTi trigger sources.
> +
> +Example:

This should be last.

> +	adc: adc@...12000 {
> +		compatible = "st,stm32f4-adc";
> +		reg = <0x40012000 0x400>;
> +		interrupts = <18>;
> +		clocks = <&rcc 0 168>;
> +		clock-names = "adc";
> +		vref-supply = <&reg_vref>;
> +		pinctrl-names = "default";
> +		pinctrl-0 = <&adc3_in8_pin>;
> +		gpios = <&gpioa 11 0>,
> +			<&gpioa 15 0>;
> +
> +		#address-cells = <1>;
> +		#size-cells = <0>;
> +
> +		adc1: adc1-master@0 {

adc@0 sufficient?

> +			#io-channel-cells = <1>;
> +			reg = <0x0>;
> +			clocks = <&rcc 0 168>;
> +			st,adc-channels = <8>;
> +		};
> +		...
> +		other adc child nodes follow...
> +	};
> +
> +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:
> +- reg: Offset of ADC instance in ADC block (e.g. may be 0x0, 0x100, 0x200).
> +- st,adc-channels: List of single-ended channels muxed for this ADC.

How many? What are valid values?

> +- #io-channel-cells = <1>: See the IIO bindings section "IIO consumers" in
> +  Documentation/devicetree/bindings/iio/iio-bindings.txt
> +
> +Optional properties:
> +- clocks: Input clock private to this ADC instance.
> +- st,injected: Use injected conversion sequence on an ADC, rather than regular.

Not sure about this one. Seems like this would either be a user choice 
or depend on what's connected to the ADC.

> +- dmas: Phandle to dma channel for this ADC instance, only for regular
> +  conversions. See ../../dma/dma.txt for details.
> +- dma-names: Must be "rx" when dmas property is being used.
> -- 
> 1.9.1
>