Re: [PATCH 6/7] ASoC: add bindings for STM32 DFSDM driver

[Jonathan Cameron <jic23@kernel.org>]

On 23/01/17 16:32, Arnaud Pouliquen wrote:
> This patch adds documentation of device tree bindings for the
> STM32 DFSDM ASoC driver.
> 
> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
> ---
>  .../devicetree/bindings/sound/st,sm32-adfsdm.txt   | 84 ++++++++++++++++++++++
>  1 file changed, 84 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/sound/st,sm32-adfsdm.txt
> 
> diff --git a/Documentation/devicetree/bindings/sound/st,sm32-adfsdm.txt b/Documentation/devicetree/bindings/sound/st,sm32-adfsdm.txt
> new file mode 100644
> index 0000000..a1d27b8
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/sound/st,sm32-adfsdm.txt
> @@ -0,0 +1,84 @@
> +STMicroelectronics STM32 ADFSDM ASoC DAI device driver.
> +
> +STM32 ADFSDM ASoC is a sigma delta audio interface for digital microphone.
> +It has to be declared in device-tree as a subnode of the DFSDM mfd node.
> +
> +It offers possibility to record several mono microphones, with an option to
> +synchronize all microphones on a main one (that must be piped to filter 0)
> +Audio interface can be exposed through the generic ASoC simple card.
> +
> +2 Dmics can be connected on one SPI interface instance n.
> +Convention is that the DMIC that strobes data on rising edge is connected to the
> +corresponding DFSDM channel n; while the Dmic that strobes data on falling edge
> +is connected to the channel n-1. Simple card property "bitclock-inversion = <1>"
> +is used to specify that microphone strobes data on falling edge.
> +
> +SPI interface allows to be scheduled by an external SPI clock. To use it
> +simple card properties "bitclock-master = <&codec>" and "system-clock-frequency"
> +have to be defined in dai-link node.
> +
> +Required properties:
> +- compatible: 	Must be "st,stm32-dfsdm-audio",
> +- reg:		Specifies the DFSDM filter instance.
> +- interrupts: 	DFSDM filter instance interrupt line.
> +- dma:		DMA controller phandle and DMA request line associated to the
> +		filter instance ( specified by the field "reg")
> +- dma-names: 	must be "rx"
> +
> +- st,input-id:		Id of the SPI/Manchester interface used.
> +- st,dai-filter-order:  SinC filter order from 0 to 5.
> +			0: FastSinC
> +			[1-5]: order 1 to 5.
> +			For audio purpose it is recommended to use order 3 to 5.
Interesting for audio you consider it feature of the hardware, but for ADC you
consider that this should be userspace controlled.
Personally I'd like to see more detail on those filters but if this is convention
in Asoc then so be it.
> +
> +Optional properties:
> + - st,dai0-synchronized: Set to 1 to synchronize DAI with DFSDM instance 0.
> +
> +Exemple of a card with 2 Dmics synchronized and connected on SPI interface 1.
Example.
> +
> +	dfsdm: dfsdm@4400D000 {
> +		dai_dfsdm0: dfsdm-audio@0 {
> +			compatible = "st,stm32-dfsdm-audio";
> +			#sound-dai-cells = <0>;
> +			reg = <0>;
> +			dmas = <&dmamux1 101 0x400 0x00>;
> +			dma-names = "rx";
> +			st,input-id = <0>;
> +			st,dai-filter-order = <5>;
> +		};
> +		dai_dfsdm1: dfsdm-audio@1 {
> +			compatible = "st,stm32-dfsdm-audio";
> +			#sound-dai-cells = <0>;
> +			reg = <0>;
> +			dmas = <&dmamux1 102 0x400 0x00>;
> +			dma-names = "rx";
> +			st,input-id = <0>;
> +			st,dai0-synchronized = <1>;
> +			st,dai-filter-order = <5>;
> +		};
> +	};
> +	sound_dfsdm_pdm {
> +		compatible = "simple-audio-card";
> +		simple-audio-card,name = "dfsdm_pdm";
> +		status = "okay";
> +
> +		dfsdm0_mic0: simple-audio-card,dai-link@0 {
> +			format = "pdm";
> +			cpu {
> +				sound-dai = <&dai_dfsdm0>;
> +			};
> +			dmic0_codec: codec {
> +				sound-dai = <&dmic0>;
> +			};
> +		};
> +		dfsdm0_mic1: simple-audio-card,dai-link@1 {
> +			format = "pdm";
> +			bitclock-inversion = <1>;
> +			cpu {
> +				sound-dai = <&dai_dfsdm1>;
> +			};
> +			codec {
> +				sound-dai = <&dmic1>;
> +			};
> +		};
> +	};
> 
Jonathan