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

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Date:   Wed, 5 Apr 2017 16:47:29 +0200
From:   Fabrice Gasnier <fabrice.gasnier@...com>
To:     Jonathan Cameron <jic23@...nel.org>, <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 04/02/2017 01:16 PM, Jonathan Cameron wrote:
> 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.
Hi Jonathan,

I'll update this description in V2

> 
>> 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.
Yes, let's discuss this on following patches.

Thanks your review,
Best Regards,
Fabrice

>> +
>> +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>;
>> +		};
>> +	};
>>
>