linux-kernel - Re: [PATCH 1/4] dt-bindings: iio: stm32-dac: Add support for STM32 DAC

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Message-ID: <a6c51b90-c14b-412c-1006-cf0dd7abda0d@kernel.org>
Date:   Sun, 2 Apr 2017 12:16:41 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Fabrice Gasnier <fabrice.gasnier@...com>, linux@...linux.org.uk,
        robh+dt@...nel.org, linux-arm-kernel@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     linux-iio@...r.kernel.org, mark.rutland@....com,
        mcoquelin.stm32@...il.com, alexandre.torgue@...com,
        lars@...afoo.de, knaack.h@....de, pmeerw@...erw.net,
        benjamin.gaignard@...aro.org, benjamin.gaignard@...com,
        linus.walleij@...aro.org, amelie.delaunay@...com
Subject: Re: [PATCH 1/4] dt-bindings: iio: stm32-dac: Add support for STM32
 DAC

On 31/03/17 12:45, Fabrice Gasnier wrote:
> Document STMicroelectronics STM32 DAC (digital-to-analog converter).
> 
> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@...com>
> ---
>  .../devicetree/bindings/iio/dac/st,stm32-dac.txt   | 56 ++++++++++++++++++++++
>  1 file changed, 56 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/dac/st,stm32-dac.txt
> 
> diff --git a/Documentation/devicetree/bindings/iio/dac/st,stm32-dac.txt b/Documentation/devicetree/bindings/iio/dac/st,stm32-dac.txt
> new file mode 100644
> index 0000000..1981983
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/dac/st,stm32-dac.txt
> @@ -0,0 +1,56 @@
> +STMicroelectronics STM32 DAC
> +
> +The STM32 DAC is a 12-bit voltage output digital-to-analog converter. The DAC
> +can be configured in 8- or 12-bit mode. In 12-bit mode, the data could be
> +left- or right-aligned.
Whilst possibly true, do we care about the alignment?  That'll all get wrapped
up in the driver.

> It has two output channels, each with its own converter.
> +It has built-in noise and triangle waveform generator and supports external
> +triggers for conversions. The DAC's output buffer allows a high drive output
> +current.
Ah.. This is going to be fun :) More unusual hardware to find in an SoC.
> +
> +Contents of a stm32 dac root node:
> +-----------------------------------
> +Required properties:
> +- compatible: Must be "st,stm32h7-dac-core".
> +- reg: Offset and length of the device's register set.
> +- clocks: Must contain an entry for pclk (which feeds the peripheral bus
> +  interface)
> +- clock-names: Must be "pclk".
> +- vref-supply: Phandle to the vref+ input analog reference supply.
> +
> +Optional properties:
> +- resets: Must contain the phandle to the reset controller.
> +- A pinctrl state named "default" for each DAC channel may be defined to set
> +  DAC_OUTx pin in mode of operation for analog output on external pin.
> +
> +Contents of a stm32 dac child node:
> +-----------------------------------
> +DAC core node should contain at least one subnode, representing a
> +DAC instance/channel available on the machine.
> +
> +Required properties:
> +- compatible: Must be "st,stm32-dac".
> +- #io-channel-cells = <1>: See the IIO bindings section "IIO consumers" in
> +  Documentation/devicetree/bindings/iio/iio-bindings.txt
> +- st,dac-channel: Must be either 1 or 2, to define channel in use (e.g.
> +  single channels: 1 or 2)
> +
> +Example:
> +	dac: dac@...07400 {
> +		compatible = "st,stm32h7-dac-core";
> +		reg = <0x40007400 0x400>;
> +		clocks = <&clk>;
> +		clock-names = "pclk";
> +		vref-supply = <&reg_vref>;
> +
> +		dac1: dac@1 {
> +			compatible = "st,stm32-dac";
> +			#io-channels-cells = <1>;
> +			st,dac-channel = <1>;
> +		};
> +
> +		dac2: dac@2 {
> +			compatible = "st,stm32-dac";
> +			#io-channels-cells = <1>;
> +			st,dac-channel = <2>;
> +		};
> +	};
>