Renesas R-Car sound

=============================================
* Modules
=============================================

Renesas R-Car and RZ/G sound is constructed from below modules
(for Gen2 or later)

 SCU		: Sampling Rate Converter Unit
  - SRC		: Sampling Rate Converter
  - CMD
   - CTU	: Channel Transfer Unit
   - MIX	: Mixer
   - DVC	: Digital Volume and Mute Function
 SSIU		: Serial Sound Interface Unit
 SSI		: Serial Sound Interface

See detail of each module's channels, connection, limitation on datasheet

=============================================
* Multi channel
=============================================

Multi channel is supported by Multi-SSI, or TDM-SSI.

 Multi-SSI	: 6ch case, you can use stereo x 3 SSI
 TDM-SSI	: 6ch case, you can use TDM

=============================================
* Enable/Disable each modules
=============================================

See datasheet to check SRC/CTU/MIX/DVC connect-limitation.
DT controls enabling/disabling module.
${LINUX}/arch/arm/boot/dts/r8a7790-lager.dts can be good example.
This is example of

Playback: [MEM] -> [SRC2] -> [DVC0] -> [SSIU0/SSI0] -> [codec]
Capture:  [MEM] <- [DVC1] <- [SRC3] <- [SSIU1/SSI1] <- [codec]

see "Example: simple sound card"

You can use below.
${LINUX}/arch/arm/boot/dts/r8a7790.dts can be good example.

	&src0	&ctu00	&mix0	&dvc0	&ssi0
	&src1	&ctu01	&mix1	&dvc1	&ssi1
	&src2	&ctu02			&ssi2
	&src3	&ctu03			&ssi3
	&src4				&ssi4
	&src5	&ctu10			&ssi5
	&src6	&ctu11			&ssi6
	&src7	&ctu12			&ssi7
	&src8	&ctu13			&ssi8
	&src9				&ssi9

=============================================
* SRC (Sampling Rate Converter)
=============================================

 [xx]Hz        [yy]Hz
 ------> [SRC] ------>

SRC can convert [xx]Hz to [yy]Hz. Then, it has below 2 modes

 Asynchronous mode:	input data / output data are based on different clocks.
			you can use this mode on Playback / Capture
 Synchronous mode:	input data / output data are based on same clocks.
			This mode will be used if system doesn't have its input clock,
			for example digital TV case.
			you can use this mode on Playback

------------------
**     Asynchronous mode
------------------

You need to use "simple-scu-audio-card" or "audio-graph-scu-card" for it.
see "Example: simple sound card for Asynchronous mode"

------------------
**     Synchronous mode
------------------

	> amixer set "SRC Out Rate" on
	> aplay xxxx.wav
	> amixer set "SRC Out Rate" 48000
	> amixer set "SRC Out Rate" 44100

=============================================
* CTU (Channel Transfer Unit)
=============================================

 [xx]ch        [yy]ch
 ------> [CTU] -------->

CTU can convert [xx]ch to [yy]ch, or exchange outputed channel.
CTU conversion needs matrix settings.
For more detail information, see below

	Renesas R-Car datasheet
	 - Sampling Rate Converter Unit (SCU)
	  - SCU Operation
	   - CMD Block
	    - Functional Blocks in CMD

	Renesas R-Car datasheet
	 - Sampling Rate Converter Unit (SCU)
	  - Register Description
	   - CTUn Scale Value exx Register (CTUn_SVxxR)

	${LINUX}/sound/soc/sh/rcar/ctu.c
	 - comment of header

You need to use "simple-scu-audio-card" or "audio-graph-scu-card" for it.
see "Example: simple sound card for channel convert"

Ex) Exchange output channel
 Input -> Output
  1ch  ->  0ch
  0ch  ->  1ch

  example of using matrix
	output 0ch = (input 0ch x 0) + (input 1ch x 1)
	output 1ch = (input 0ch x 1) + (input 1ch x 0)

	amixer set "CTU Reset" on
	amixer set "CTU Pass" 9,10
	amixer set "CTU SV0" 0,4194304
	amixer set "CTU SV1" 4194304,0

 example of changing connection
	amixer set "CTU Reset" on
	amixer set "CTU Pass" 2,1

=============================================
* MIX (Mixer)
=============================================

MIX merges 2 sounds path. You can see 2 sound interface on system,
and these sounds will be merged by MIX.

	aplay -D plughw:0,0 xxxx.wav &
	aplay -D plughw:0,1 yyyy.wav

You need to use "simple-scu-audio-card" or "audio-graph-scu-card" for it.
Ex)
	[MEM] -> [SRC1] -> [CTU02] -+-> [MIX0] -> [DVC0] -> [SSI0]
	                            |
	[MEM] -> [SRC2] -> [CTU03] -+

see "Example: simple sound card for MIXer"

=============================================
* DVC (Digital Volume and Mute Function)
=============================================

DVC controls Playback/Capture volume.

Playback Volume
	amixer set "DVC Out" 100%

Capture Volume
	amixer set "DVC In" 100%

Playback Mute
	amixer set "DVC Out Mute" on

Capture Mute
	amixer set "DVC In Mute" on

Volume Ramp
	amixer set "DVC Out Ramp Up Rate"   "0.125 dB/64 steps"
	amixer set "DVC Out Ramp Down Rate" "0.125 dB/512 steps"
	amixer set "DVC Out Ramp" on
	aplay xxx.wav &
	amixer set "DVC Out"  80%  // Volume Down
	amixer set "DVC Out" 100%  // Volume Up

=============================================
* SSIU (Serial Sound Interface Unit)
=============================================

SSIU can avoid some under/over run error, because it has some buffer.
But you can't use it if SSI was PIO mode.
In DMA mode, you can select not to use SSIU by using "no-busif" via SSI.

SSIU handles BUSIF which will be used for TDM Split mode.
This driver is assuming that audio-graph card will be used.

TDM Split mode merges 4 sounds. You can see 4 sound interface on system,
and these sounds will be merged SSIU/SSI.

	aplay -D plughw:0,0 xxxx.wav &
	aplay -D plughw:0,1 xxxx.wav &
	aplay -D plughw:0,2 xxxx.wav &
	aplay -D plughw:0,3 xxxx.wav

	          2ch                     8ch
	[MEM] -> [SSIU 30] -+-> [SSIU 3] --> [Codec]
	          2ch       |
	[MEM] -> [SSIU 31] -+
	          2ch       |
	[MEM] -> [SSIU 32] -+
	          2ch       |
	[MEM] -> [SSIU 33] -+

see "Example: simple sound card for TDM Split"

=============================================
* SSI (Serial Sound Interface)
=============================================

**  PIO mode

You can use PIO mode which is for connection check by using.
Note: The system will drop non-SSI modules in PIO mode
even though if DT is selecting other modules.

	&ssi0 {
		pio-transfer
	};

** DMA mode without SSIU

You can use DMA without SSIU.
Note: under/over run, or noise are likely to occur

	&ssi0 {
		no-busif;
	};

** PIN sharing

Each SSI can share WS pin. It is based on platform.
This is example if SSI1 want to share WS pin with SSI0

	&ssi1 {
		shared-pin;
	};

** Multi-SSI

You can use Multi-SSI.
This is example of SSI0/SSI1/SSI2 (= for 6ch)

see "Example: simple sound card for Multi channel"

** TDM-SSI

You can use TDM with SSI.
This is example of TDM 6ch.
Driver can automatically switches TDM <-> stereo mode in this case.

see "Example: simple sound card for TDM"

=============================================
Required properties:
=============================================

- compatible			: "renesas,rcar_sound-<soctype>", fallbacks
				  "renesas,rcar_sound-gen1" if generation1, and
				  "renesas,rcar_sound-gen2" if generation2 (or RZ/G1)
				  "renesas,rcar_sound-gen3" if generation3 (or RZ/G2)
				  Examples with soctypes are:
				    - "renesas,rcar_sound-r8a7743" (RZ/G1M)
				    - "renesas,rcar_sound-r8a7744" (RZ/G1N)
				    - "renesas,rcar_sound-r8a7745" (RZ/G1E)
				    - "renesas,rcar_sound-r8a77470" (RZ/G1C)
				    - "renesas,rcar_sound-r8a774a1" (RZ/G2M)
				    - "renesas,rcar_sound-r8a774b1" (RZ/G2N)
				    - "renesas,rcar_sound-r8a774c0" (RZ/G2E)
				    - "renesas,rcar_sound-r8a7778" (R-Car M1A)
				    - "renesas,rcar_sound-r8a7779" (R-Car H1)
				    - "renesas,rcar_sound-r8a7790" (R-Car H2)
				    - "renesas,rcar_sound-r8a7791" (R-Car M2-W)
				    - "renesas,rcar_sound-r8a7793" (R-Car M2-N)
				    - "renesas,rcar_sound-r8a7794" (R-Car E2)
				    - "renesas,rcar_sound-r8a7795" (R-Car H3)
				    - "renesas,rcar_sound-r8a7796" (R-Car M3-W)
				    - "renesas,rcar_sound-r8a77965" (R-Car M3-N)
				    - "renesas,rcar_sound-r8a77990" (R-Car E3)
				    - "renesas,rcar_sound-r8a77995" (R-Car D3)
- reg				: Should contain the register physical address.
				  required register is
				   SRU/ADG/SSI      if generation1
				   SRU/ADG/SSIU/SSI/AUDIO-DMAC-periperi if generation2/generation3
				   Select extended AUDIO-DMAC-periperi address if SoC has it,
				   otherwise select normal AUDIO-DMAC-periperi address.
- reg-names			: Should contain the register names.
				   scu/adg/ssi	if generation1
				   scu/adg/ssiu/ssi/audmapp if generation2/generation3
- rcar_sound,ssi		: Should contain SSI feature.
				  The number of SSI subnode should be same as HW.
				  see below for detail.
- rcar_sound,ssiu		: Should contain SSIU feature.
				  The number of SSIU subnode should be same as HW.
				  see below for detail.
- rcar_sound,src		: Should contain SRC feature.
				  The number of SRC subnode should be same as HW.
				  see below for detail.
- rcar_sound,ctu		: Should contain CTU feature.
				  The number of CTU subnode should be same as HW.
				  see below for detail.
- rcar_sound,mix		: Should contain MIX feature.
				  The number of MIX subnode should be same as HW.
				  see below for detail.
- rcar_sound,dvc		: Should contain DVC feature.
				  The number of DVC subnode should be same as HW.
				  see below for detail.
- rcar_sound,dai		: DAI contents.
				  The number of DAI subnode should be same as HW.
				  see below for detail.
- #sound-dai-cells		: it must be 0 if your system is using single DAI
				  it must be 1 if your system is using multi  DAI
- clocks			: References to SSI/SRC/MIX/CTU/DVC/AUDIO_CLK clocks.
- clock-names			: List of necessary clock names.
				  "ssi-all", "ssi.X", "src.X", "mix.X", "ctu.X",
				  "dvc.X", "clk_a", "clk_b", "clk_c", "clk_i"

Optional properties:
- #clock-cells			: it must be 0 if your system has audio_clkout
				  it must be 1 if your system has audio_clkout0/1/2/3
- clock-frequency		: for all audio_clkout0/1/2/3
- clkout-lr-asynchronous	: boolean property. it indicates that audio_clkoutn
				  is asynchronizes with lr-clock.
- resets			: References to SSI resets.
- reset-names			: List of valid reset names.
				  "ssi-all", "ssi.X"

SSI subnode properties:
- interrupts			: Should contain SSI interrupt for PIO transfer
- shared-pin			: if shared clock pin
- pio-transfer			: use PIO transfer mode
- no-busif			: BUSIF is not ussed when [mem -> SSI] via DMA case
- dma				: Should contain Audio DMAC entry
- dma-names			: SSI  case "rx"  (=playback), "tx"  (=capture)
				  Deprecated: see SSIU subnode properties
				  SSIU case "rxu" (=playback), "txu" (=capture)

SSIU subnode properties:
- dma				: Should contain Audio DMAC entry
- dma-names			: "rx" (=playback), "tx" (=capture)

SRC subnode properties:
- dma				: Should contain Audio DMAC entry
- dma-names			: "rx" (=playback), "tx" (=capture)

DVC subnode properties:
- dma				: Should contain Audio DMAC entry
- dma-names			: "tx" (=playback/capture)

DAI subnode properties:
- playback			: list of playback modules
- capture			: list of capture  modules


=============================================
Example:
=============================================

rcar_sound: sound@ec500000 {
	#sound-dai-cells = <1>;
	compatible = "renesas,rcar_sound-r8a7791", "renesas,rcar_sound-gen2";
	reg =	<0 0xec500000 0 0x1000>, /* SCU */
		<0 0xec5a0000 0 0x100>,  /* ADG */
		<0 0xec540000 0 0x1000>, /* SSIU */
		<0 0xec541000 0 0x1280>, /* SSI */
		<0 0xec740000 0 0x200>;  /* Audio DMAC peri peri*/
	reg-names = "scu", "adg", "ssiu", "ssi", "audmapp";

	clocks = <&mstp10_clks R8A7790_CLK_SSI_ALL>,
		<&mstp10_clks R8A7790_CLK_SSI9>, <&mstp10_clks R8A7790_CLK_SSI8>,
		<&mstp10_clks R8A7790_CLK_SSI7>, <&mstp10_clks R8A7790_CLK_SSI6>,
		<&mstp10_clks R8A7790_CLK_SSI5>, <&mstp10_clks R8A7790_CLK_SSI4>,
		<&mstp10_clks R8A7790_CLK_SSI3>, <&mstp10_clks R8A7790_CLK_SSI2>,
		<&mstp10_clks R8A7790_CLK_SSI1>, <&mstp10_clks R8A7790_CLK_SSI0>,
		<&mstp10_clks R8A7790_CLK_SCU_SRC9>, <&mstp10_clks R8A7790_CLK_SCU_SRC8>,
		<&mstp10_clks R8A7790_CLK_SCU_SRC7>, <&mstp10_clks R8A7790_CLK_SCU_SRC6>,
		<&mstp10_clks R8A7790_CLK_SCU_SRC5>, <&mstp10_clks R8A7790_CLK_SCU_SRC4>,
		<&mstp10_clks R8A7790_CLK_SCU_SRC3>, <&mstp10_clks R8A7790_CLK_SCU_SRC2>,
		<&mstp10_clks R8A7790_CLK_SCU_SRC1>, <&mstp10_clks R8A7790_CLK_SCU_SRC0>,
		<&mstp10_clks R8A7790_CLK_SCU_DVC0>, <&mstp10_clks R8A7790_CLK_SCU_DVC1>,
		<&audio_clk_a>, <&audio_clk_b>, <&audio_clk_c>, <&m2_clk>;
	clock-names = "ssi-all",
			"ssi.9", "ssi.8", "ssi.7", "ssi.6", "ssi.5",
			"ssi.4", "ssi.3", "ssi.2", "ssi.1", "ssi.0",
			"src.9", "src.8", "src.7", "src.6", "src.5",
			"src.4", "src.3", "src.2", "src.1", "src.0",
			"dvc.0", "dvc.1",
			"clk_a", "clk_b", "clk_c", "clk_i";

	rcar_sound,dvc {
		dvc0: dvc-0 {
			dmas = <&audma0 0xbc>;
			dma-names = "tx";
		};
		dvc1: dvc-1 {
			dmas = <&audma0 0xbe>;
			dma-names = "tx";
		};
	};

	rcar_sound,mix {
		mix0: mix-0 { };
		mix1: mix-1 { };
	};

	rcar_sound,ctu {
		ctu00: ctu-0 { };
		ctu01: ctu-1 { };
		ctu02: ctu-2 { };
		ctu03: ctu-3 { };
		ctu10: ctu-4 { };
		ctu11: ctu-5 { };
		ctu12: ctu-6 { };
		ctu13: ctu-7 { };
	};

	rcar_sound,src {
		src0: src-0 {
			interrupts = <0 352 IRQ_TYPE_LEVEL_HIGH>;
			dmas = <&audma0 0x85>, <&audma1 0x9a>;
			dma-names = "rx", "tx";
		};
		src1: src-1 {
			interrupts = <0 353 IRQ_TYPE_LEVEL_HIGH>;
			dmas = <&audma0 0x87>, <&audma1 0x9c>;
			dma-names = "rx", "tx";
		};
		src2: src-2 {
			interrupts = <0 354 IRQ_TYPE_LEVEL_HIGH>;
			dmas = <&audma0 0x89>, <&audma1 0x9e>;
			dma-names = "rx", "tx";
		};
		src3: src-3 {
			interrupts = <0 355 IRQ_TYPE_LEVEL_HIGH>;
			dmas = <&audma0 0x8b>, <&audma1 0xa0>;
			dma-names = "rx", "tx";
		};
		src4: src-4 {
			interrupts = <0 356 IRQ_TYPE_LEVEL_HIGH>;
			dmas = <&audma0 0x8d>, <&audma1 0xb0>;
			dma-names = "rx", "tx";
		};
		src5: src-5 {
			interrupts = <0 357 IRQ_TYPE_LEVEL_HIGH>;
			dmas = <&audma0 0x8f>, <&audma1 0xb2>;
			dma-names = "rx", "tx";
		};
		src6: src-6 {
			interrupts = <0 358 IRQ_TYPE_LEVEL_HIGH>;
			dmas = <&audma0 0x91>, <&audma1 0xb4>;
			dma-names = "rx", "tx";
		};
		src7: src-7 {
			interrupts = <0 359 IRQ_TYPE_LEVEL_HIGH>;
			dmas = <&audma0 0x93>, <&audma1 0xb6>;
			dma-names = "rx", "tx";
		};
		src8: src-8 {
			interrupts = <0 360 IRQ_TYPE_LEVEL_HIGH>;
			dmas = <&audma0 0x95>, <&audma1 0xb8>;
			dma-names = "rx", "tx";
		};
		src9: src-9 {
			interrupts = <0 361 IRQ_TYPE_LEVEL_HIGH>;
			dmas = <&audma0 0x97>, <&audma1 0xba>;
			dma-names = "rx", "tx";
		};
	};

	rcar_sound,ssiu {
		ssiu00: ssiu-0 {
			dmas = <&audma0 0x15>, <&audma1 0x16>;
			dma-names = "rx", "tx";
		};
		ssiu01: ssiu-1 {
			dmas = <&audma0 0x35>, <&audma1 0x36>;
			dma-names = "rx", "tx";
		};

		...

		ssiu95: ssiu-49 {
			dmas = <&audma0 0xA5>, <&audma1 0xA6>;
			dma-names = "rx", "tx";
		};
		ssiu96: ssiu-50 {
			dmas = <&audma0 0xA7>, <&audma1 0xA8>;
			dma-names = "rx", "tx";
		};
		ssiu97: ssiu-51 {
			dmas = <&audma0 0xA9>, <&audma1 0xAA>;
			dma-names = "rx", "tx";
		};
	};

	rcar_sound,ssi {
		ssi0: ssi-0 {
			interrupts = <0 370 IRQ_TYPE_LEVEL_HIGH>;
			dmas = <&audma0 0x01>, <&audma1 0x02>;
			dma-names = "rx", "tx";
		};
		ssi1: ssi-1 {
			interrupts = <0 371 IRQ_TYPE_LEVEL_HIGH>;
			dmas = <&audma0 0x03>, <&audma1 0x04>;
			dma-names = "rx", "tx";
		};

		...

		ssi8: ssi-8 {
			interrupts = <0 378 IRQ_TYPE_LEVEL_HIGH>;
			dmas = <&audma0 0x11>, <&audma1 0x12>;
			dma-names = "rx", "tx";
		};
		ssi9: ssi-9 {
			interrupts = <0 379 IRQ_TYPE_LEVEL_HIGH>;
			dmas = <&audma0 0x13>, <&audma1 0x14>;
			dma-names = "rx", "tx";
		};
	};

	rcar_sound,dai {
		dai0 {
			playback = <&ssi5 &src5>;
			capture  = <&ssi6>;
		};
		dai1 {
			playback = <&ssi3>;
		};
		dai2 {
			capture  = <&ssi4>;
		};
		dai3 {
			playback = <&ssi7>;
		};
		dai4 {
			capture  = <&ssi8>;
		};
	};
};

=============================================
Example: simple sound card
=============================================

	rsnd_ak4643: sound {
		compatible = "simple-audio-card";

		simple-audio-card,format = "left_j";
		simple-audio-card,bitclock-master = <&sndcodec>;
		simple-audio-card,frame-master = <&sndcodec>;

		sndcpu: simple-audio-card,cpu {
			sound-dai = <&rcar_sound>;
		};

		sndcodec: simple-audio-card,codec {
			sound-dai = <&ak4643>;
			clocks = <&audio_clock>;
		};
	};

&rcar_sound {
	pinctrl-0 = <&sound_pins &sound_clk_pins>;
	pinctrl-names = "default";

	/* Single DAI */
	#sound-dai-cells = <0>;


	rcar_sound,dai {
		dai0 {
			playback = <&ssi0 &src2 &dvc0>;
			capture  = <&ssi1 &src3 &dvc1>;
		};
	};
};

&ssi1 {
	shared-pin;
};

=============================================
Example: simple sound card for Asynchronous mode
=============================================

sound {
	compatible = "simple-scu-audio-card";
	...
	/*
	 * SRC Asynchronous mode setting
	 * Playback:
	 * All input data will be converted to 48kHz
	 * Capture:
	 * Inputed 48kHz data will be converted to
	 * system specified Hz
	 */
	simple-audio-card,convert-rate = <48000>;
	...
	simple-audio-card,cpu {
		sound-dai = <&rcar_sound>;
	};
	simple-audio-card,codec {
		...
	};
};

=============================================
Example: simple sound card for channel convert
=============================================

sound {
	compatible = "simple-scu-audio-card";
	...
	/*
	 * CTU setting
	 * All input data will be converted to 2ch
	 * as output data
	 */
	simple-audio-card,convert-channels = <2>;
	...
	simple-audio-card,cpu {
		sound-dai = <&rcar_sound>;
	};
	simple-audio-card,codec {
		...
	};
};

=============================================
Example: simple sound card for MIXer
=============================================

sound {
	compatible = "simple-scu-audio-card";
	...
	simple-audio-card,cpu@0 {
		sound-dai = <&rcar_sound 0>;
	};
	simple-audio-card,cpu@1 {
		sound-dai = <&rcar_sound 1>;
	};
	simple-audio-card,codec {
		...
	};
};

&rcar_sound {
	...
	rcar_sound,dai {
		dai0 {
			playback = <&src1 &ctu02 &mix0 &dvc0 &ssi0>;
		};
		dai1 {
			playback = <&src2 &ctu03 &mix0 &dvc0 &ssi0>;
		};
	};
};

=============================================
Example: simple sound card for TDM
=============================================

rsnd_tdm: sound {
	compatible = "simple-audio-card";

	simple-audio-card,format = "left_j";
	simple-audio-card,bitclock-master = <&sndcodec>;
	simple-audio-card,frame-master = <&sndcodec>;

	sndcpu: simple-audio-card,cpu {
		sound-dai = <&rcar_sound>;
		dai-tdm-slot-num = <6>;
	};

	sndcodec: simple-audio-card,codec {
		sound-dai = <&xxx>;
	};
};

=============================================
Example: simple sound card for TDM Split
=============================================

sound_card: sound {
	compatible = "audio-graph-scu-card";
	prefix = "xxxx";
	routing = "xxxx Playback", "DAI0 Playback",
		  "xxxx Playback", "DAI1 Playback",
		  "xxxx Playback", "DAI2 Playback",
		  "xxxx Playback", "DAI3 Playback";
	convert-channels = <8>; /* TDM Split */

	dais = <&rsnd_port0     /* playback ch1/ch2 */
		&rsnd_port1     /* playback ch3/ch4 */
		&rsnd_port2     /* playback ch5/ch6 */
		&rsnd_port3     /* playback ch7/ch8 */
		>;
};

audio-codec {
	...
	port {
		codec_0: endpoint@1 {
			remote-endpoint = <&rsnd_ep0>;
		};
		codec_1: endpoint@2 {
			remote-endpoint = <&rsnd_ep1>;
		};
		codec_2: endpoint@3 {
			remote-endpoint = <&rsnd_ep2>;
		};
		codec_3: endpoint@4 {
			remote-endpoint = <&rsnd_ep3>;
		};
	};
};

&rcar_sound {
	...
	ports {
		rsnd_port0: port@0 {
			rsnd_ep0: endpoint {
				remote-endpoint = <&codec_0>;
				...
				playback = <&ssiu30 &ssi3>;
			};
		};
		rsnd_port1: port@1 {
			rsnd_ep1: endpoint {
				remote-endpoint = <&codec_1>;
				...
				playback = <&ssiu31 &ssi3>;
			};
		};
		rsnd_port2: port@2 {
			rsnd_ep2: endpoint {
				remote-endpoint = <&codec_2>;
				...
				playback = <&ssiu32 &ssi3>;
			};
		};
		rsnd_port3: port@3 {
			rsnd_ep3: endpoint {
				remote-endpoint = <&codec_3>;
				...
				playback = <&ssiu33 &ssi3>;
			};
		};
	};
};

=============================================
Example: simple sound card for Multi channel
=============================================

&rcar_sound {
	pinctrl-0 = <&sound_pins &sound_clk_pins>;
	pinctrl-names = "default";

	/* Single DAI */
	#sound-dai-cells = <0>;


	rcar_sound,dai {
		dai0 {
			playback = <&ssi0 &ssi1 &ssi2 &src0 &dvc0>;
		};
	};
};