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What:		/sys/bus/iio/devices/iio:deviceX/in_voltage_spi_clk_freq

KernelVersion:	4.14

Contact:	arnaud.pouliquen@st.com

Description:

		For audio purpose only.

		Used by audio driver to set/get the spi input frequency.

		This is mandatory if DFSDM is slave on SPI bus, to

		provide information on the SPI clock frequency during runtime

		Notice that the SPI frequency should be a multiple of sample

		frequency to ensure the precision.

		if DFSDM input is SPI master

			Reading  SPI clkout frequency,

			error on writing

		If DFSDM input is SPI Slave:

			Reading returns value previously set.

			Writing value before starting conversions.

 No newline at end of file

Device-Tree bindings for sigma delta modulator

Required properties:

- compatible: should be "ads1201", "sd-modulator". "sd-modulator" can be use

	as a generic SD modulator if modulator not specified in compatible list.

- #io-channel-cells = <1>: See the IIO bindings section "IIO consumers".

Example node:

	ads1202: adc@0 {

		compatible = "sd-modulator";

		#io-channel-cells = <1>;

	};

STMicroelectronics STM32 DFSDM ADC device driver

STM32 DFSDM ADC is a sigma delta analog-to-digital converter dedicated to

interface external sigma delta modulators to STM32 micro controllers.

It is mainly targeted for:

- Sigma delta modulators (motor control, metering...)

- PDM microphones (audio digital microphone)

It features up to 8 serial digital interfaces (SPI or Manchester) and

up to 4 filters on stm32h7.

Each child node match with a filter instance.

Contents of a STM32 DFSDM root node:

------------------------------------

Required properties:

- compatible: Should be "st,stm32h7-dfsdm".

- 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.

- #interrupt-cells = <1>;

- #address-cells = <1>;

- #size-cells = <0>;

Optional properties:

- spi-max-frequency: Requested only 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, SPI 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-dmic" for audio digital microphone.

- reg: Specifies the DFSDM filter instance used.

- interrupts: IRQ lines connected to each DFSDM filter instance.

- st,adc-channels:	List of single-ended channels muxed for this ADC.

			valid values:

				"st,stm32h7-dfsdm" compatibility: 0 to 7.

- st,adc-channel-names:	List of single-ended channel names.

- st,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.

- #io-channel-cells = <1>: See the IIO bindings section "IIO consumers".

Required properties for "st,stm32-dfsdm-adc" compatibility:

- io-channels: From common IIO binding. Used to pipe external sigma delta

		modulator or internal ADC output to DFSDM channel.

		This is not required for "st,stm32-dfsdm-pdm" compatibility as

		PDM microphone is binded in Audio DT node.

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.

			- "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.

			  - "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.

		   Used for multi microphones synchronization.

Example of a sigma delta adc connected on DFSDM SPI port 0

and a pdm microphone connected on DFSDM SPI port 1:

	ads1202: simple_sd_adc@0 {

		compatible = "ads1202";

		#io-channel-cells = <1>;

	};

	dfsdm: dfsdm@40017000 {

		compatible = "st,stm32h7-dfsdm";

		reg = <0x40017000 0x400>;

		clocks = <&rcc DFSDM1_CK>;

		clock-names = "dfsdm";

		#interrupt-cells = <1>;

		#address-cells = <1>;

		#size-cells = <0>;

		dfsdm_adc0: filter@0 {

			compatible = "st,stm32-dfsdm-adc";

			#io-channel-cells = <1>;

			reg = <0>;

			interrupts = <110>;

			st,adc-channels = <0>;

			st,adc-channel-names = "sd_adc0";

			st,adc-channel-types = "SPI_F";

			st,adc-channel-clk-src = "CLKOUT";

			io-channels = <&ads1202 0>;

			st,filter-order = <3>;

		};

		dfsdm_pdm1: filter@1 {

			compatible = "st,stm32-dfsdm-dmic";

			reg = <1>;

			interrupts = <111>;

			dmas = <&dmamux1 102 0x400 0x00>;

			dma-names = "rx";

			st,adc-channels = <1>;

			st,adc-channel-names = "dmic1";

			st,adc-channel-types = "SPI_R";

			st,adc-channel-clk-src = "CLKOUT";

			st,filter-order = <5>;

		};

	}

Maxim Integrated MAX98373 Speaker Amplifier

This device supports I2C.

Required properties:

 - compatible : "maxim,max98373"

 - reg : the I2C address of the device.

Optional properties:

  - maxim,vmon-slot-no : slot number used to send voltage information

                   or in inteleave mode this will be used as

                   interleave slot.

                   slot range : 0 ~ 15,  Default : 0

  - maxim,imon-slot-no : slot number used to send current information

                   slot range : 0 ~ 15,  Default : 0

  - maxim,spkfb-slot-no : slot number used to send speaker feedback information

                   slot range : 0 ~ 15,  Default : 0

  - maxim,interleave-mode : For cases where a single combined channel

		   for the I/V sense data is not sufficient, the device can also be configured

		   to share a single data output channel on alternating frames.

		   In this configuration, the current and voltage data will be frame interleaved

		   on a single output channel.

                   Boolean, define to enable the interleave mode, Default : false

Example:

codec: max98373@31 {

   compatible = "maxim,max98373";

   reg = <0x31>;

   maxim,vmon-slot-no = <0>;

   maxim,imon-slot-no = <1>;

   maxim,spkfb-slot-no = <2>;

   maxim,interleave-mode;

};

===========

HW consumer

===========

An IIO device can be directly connected to another device in hardware. in this

case the buffers between IIO provider and IIO consumer are handled by hardware.

The Industrial I/O HW consumer offers a way to bond these IIO devices without

software buffer for data. The implementation can be found under

:file:`drivers/iio/buffer/hw-consumer.c`

* struct :c:type:`iio_hw_consumer` — Hardware consumer structure

* :c:func:`iio_hw_consumer_alloc` — Allocate IIO hardware consumer

* :c:func:`iio_hw_consumer_free` — Free IIO hardware consumer

* :c:func:`iio_hw_consumer_enable` — Enable IIO hardware consumer

* :c:func:`iio_hw_consumer_disable` — Disable IIO hardware consumer

HW consumer setup

=================

As standard IIO device the implementation is based on IIO provider/consumer.

A typical IIO HW consumer setup looks like this::

	static struct iio_hw_consumer *hwc;

	static const struct iio_info adc_info = {

		.read_raw = adc_read_raw,

	};

	static int adc_read_raw(struct iio_dev *indio_dev,

				struct iio_chan_spec const *chan, int *val,

				int *val2, long mask)

	{

		ret = iio_hw_consumer_enable(hwc);

		/* Acquire data */

		ret = iio_hw_consumer_disable(hwc);

	}

	static int adc_probe(struct platform_device *pdev)

	{

		hwc = devm_iio_hw_consumer_alloc(&iio->dev);

	}

More details

============

.. kernel-doc:: include/linux/iio/hw-consumer.h

.. kernel-doc:: drivers/iio/buffer/industrialio-hw-consumer.c

   :export: