[RFC v2 6/7] IIO: add bindings for stm32 DFSDM filter

[Arnaud Pouliquen]

On 02/19/2017 04:00 PM, Jonathan Cameron wrote:
> On 13/02/17 16:38, Arnaud Pouliquen wrote:
>> Add bindings that describe Digital Filter for Sigma Delta
>> Modulators. DFSDM allows to connect sigma delta
>> modulators and/or PDM microphones.
>>
>> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen at st.com>
>> ---
>>  .../bindings/iio/adc/st,stm32-dfsdm-adc.txt        | 125 +++++++++++++++++++++
>>  1 file changed, 125 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/iio/adc/st,stm32-dfsdm-adc.txt
>>
>> diff --git a/Documentation/devicetree/bindings/iio/adc/st,stm32-dfsdm-adc.txt b/Documentation/devicetree/bindings/iio/adc/st,stm32-dfsdm-adc.txt
>> new file mode 100644
>> index 0000000..83937cb
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/iio/adc/st,stm32-dfsdm-adc.txt
>> @@ -0,0 +1,125 @@
>> +STMicroelectronics STM32 DFSDM ADC device driver
>> +
>> +
>> +STM32 DFSDM ADC is a sigma delta analog-to-digital converter dedicted to
>> +interface external sigma delta modulators to stm32 micro controlers.
>> +it is mainly targeted for:
>> +- Sigma delta modulators ( motor control, metering...)
>> +- PDM microphones ( audio digital microphone)
>> +
>> +It featured with up to 8 serial digital interface (SPI or Manchester) and
>> +up to 4 filters.
>> +
>> +Each instance of the sub-drivers uses one filter instance.
>> +
>> +Contents of a stm32 dfsdmc root node:
>> +-------------------------------------
>> +Required properties:
>> +- compatible: Should be "st,stm32-dfsdm-adc".
>> +- reg: Offset and length of the DFSDM block register set.
>> +- clocks: IP and serial interfaces clocking. Should be set according
>> +		to rcc clock ID and "clock-names".
>> +- clock-names: Input clock name "dfsdm" must be defined,
>> +		"audio" is optional. If defined CLKOUT is based on the audio
>> +		clock, else "dfsdm" is used.
>> +- clocks: Clock for the analog circuitry (common to all ADCs).
>> +- clock-names: Must be "adc".
>> +
>> +Optional properties:
>> +- st,clkout-freq: needed for SPI master mode
>> +		  SPI clock OUT frequency (Hz).This clock must be set according
>> +		  to "clock" property. Frequency must be a multiple of the rcc
>> +		  clock frequency. If not, clkout frequency will not be
>> +		  accurate.
>> +
>> +Contents of a stm32 DFSDM child nodes:
>> +----------------------------------------
>> +
>> +Required properties:
>> +- compatible: Must be:
>> +	"st,stm32-dfsdm-adc" for sigma delta ADCs
>> +	"st,stm32-dfsdm-pdm" for audio digital microphone.
>> +- reg: Specifies the DFSDM filter instance.
>> +- interrupts: IRQ lines connected to each DFSDM filter instance.
>> +- st,adc-channels:	List of single-ended channels muxed for this ADC.
>> +- st,adc-channel-names:	List of single-ended channels Name.
>> +- 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.
>> +
>> +Required properties for "st,stm32-dfsdm-adc" compatibility:
>> +- #io-channel-cells = <1>: See the IIO bindings section "IIO consumers".
>> +- io-channels: from common iio binding. use to pipe external sigma delta
>> +		modulator or internal ADC output to dfsdm channel.
>> +
>> +Required properties for "st,stm32-dfsdm-pdm" compatibility:
>> +- #sound-dai-cells: must be set to 0.
>> +- dma: DMA controller phandle and DMA request line associated to the
>> +		filter instance ( specified by the field "reg")
>> +- dma-names: must be "rx"
>> +
>> +Optional properties:
>> +- st,adc-channel-types:	Single-ended channel input type. Default value is 0.
>> +			- "SPI_R": SPI with data on rising edge (default)
>> +			- "SPI_F": SPI with data on falling edge
>> +			- "MANCH_R": manchester codec, rising edge = logic 0
>> +			- "MANCH_F": manchester codec, falling edge = logic 1
>> +- st,adc-channel-clk-src: Conversion clock source. default value is 1.
>> +			  - "CLKIN": External SPI clock (CLKIN x)
>> +			  - "CLKOUT": internal SPI clock (CLKOUT) (default)
>> +			  - "CLKOUT_F": internal SPI clock divided by 2 (falling edge).
>> +			  - "CLKOUT_R": internal SPI clock divided by 2 (rising edge).
>> +
>> +- st,adc-alt-channel: Must be defined if Two sigma delta modulator are
>> +			  connected on same SPI input.
>> +			  If not set channel n is connected to SPI input n.
>> +			  If set channel n is connected to SPI input n + 1.
>> +
>> +- st,filter0-sync: Set to 1 to synchronize with DFSDM filter instance 0.
>> +		   to used for multi microphone synchronization.
>> +
>> +Example of a sigma delta adc purpose:
>> +	ads1202: simple_sd_adc at 0 {
>> +		compatible = "sd-modulator";
> This suggests to me that we ought to have a primary compatible of the actual part
> number.  Down the line I suspect we will want to distinguish between the different
> ADCs and it's kind of easier if we do it from the start.  May not be obvious
> later which the 'default sd-modulator' is.
Not sure to understand your point... you mean use ADC name instead, for
compatibility as suggested by Rob?

>> +		#io-channel-cells = <1>;
>> +		status = "okay";
>> +	};
>> +	dfsdm: dfsdm at 40017000 {
>> +		compatible = "st,stm32h7-dfsdm";
>> +		reg = <0x40017000 0x400>;
>> +		clocks = <&timer_clk>;
>> +		clock-names = "dfsdm";
>> +
>> +		dfsdm_adc0: dfsdm-adc0 at 0 {
>> +			compatible = "st,stm32-dfsdm-adc";
>> +			#io-channel-cells = <1>;
>> +			reg = <0>;
>> +			interrupts = <110>;
>> +			st,adc-channels = <0>;
>> +			st,adc-channel-names = "in0";
>> +			st,adc-channel-types = "SPI_R";
>> +			st,adc-channel-clk-src = "CLKOUT";
>> +			io-channels = <&ads1202 0>;
>> +	};
>> +
>> +Example of a pdm microphone purpose:
> Is there nothing about the particular pdm microphone that is
> worth giving it an explicit representation in the device
> tree?  I've no idea having never used one!
>> +	dfsdm: dfsdm at 40017000 {
>> +		compatible = "st,stm32h7-dfsdm";
>> +		reg = <0x40017000 0x400>;
>> +		clocks = <&timer_clk>;
>> +		clock-names = "dfsdm";
>> +
>> +		dfsdm_pdm0: dfsdm-pdm at 0 {
>> +			compatible = "st,stm32-dfsdm-pdm";
>> +			#sound-dai-cells = <0>;
>> +			reg = <0>;
>> +			interrupts = <110>;
>> +			dmas = <&dmamux1 102 0x400 0x00>;
>> +			dma-names = "rx";
>> +			st,adc-channels = <0>;
>> +			st,adc-channel-names = "pdm1";
>> +			st,adc-channel-types = "SPI_R";
>> +			st,adc-channel-clk-src = "CLKOUT";
>> +		};
>> +	}
>>
> 
Here is a way to use it in device tree.
- dmic_0 is an ASOC generic device that handles the PDM microphone
- dai-link allows to bind the DFSDM with the SD-modulator in ALSA card
declaration.

	dmic0: dmic_0 at 0 {
		compatible = "dmic-codec";
		#sound-dai-cells = <0>;

		status = "okay";
	};

	sound_dfsdm_pdm {
		compatible = "simple-audio-card";
		simple-audio-card,name = "dfsdm_pdm";
		status = "okay";

		dfsdm0_mic0: simple-audio-card,dai-link at 0 {
			format = "pdm";
			bitclock-master = <&dmic0_codec>;
			cpu {
				system-clock-frequency= <2480000>;
				sound-dai = <&dfsdm_pdm0>;
			};
			dmic0_codec: codec {
				sound-dai = <&dmic0>;
			};
		};
	};
};