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

[Arnaud Pouliquen]

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";
+		#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:
+	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";
+		};
+	}
-- 
1.9.1