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

[Fabrice Gasnier]

On 10/31/2016 04:02 AM, Rob Herring wrote:
> 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@xxxxxx>
> > ---
> >   .../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.
Hi Rob,

I'll fix this.
> > +	adc: adc@40012000 {
> > +		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?
Yes, if you agree, I'd go for adc1@0, adc2@100, adc3@200, to reflect reg 
property for child node.
Is it ok from your point of view ?

> > +			#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?
stm32f4 can have up to 19 channels, numbered from 0 to 18 to match with 
reference manual.
I'll add this.
> > +- #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.
It's related to ADC sequencer, and the way it's being configured/used 
(see above paragraph on regular/injected).
This is not related to what's connected to adc inputs.
As suggested by Jonathan, I think I'll drop injected support for now, to 
simplify the driver and review.

Thanks,
Best Regards,
Fabrice
> > +- 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