Re: How do I set up multiple codecs on one I2S - without TDM?

1 Aug 2023

      I return days later with an answer, so I shall try and answer my own email.
On Wed, Jul 26, 2023 at 08:48:18AM +1000, John Watts wrote:
...
So my questions are:

How do I express this in terms of ALSA and sound card concepts?
How do I express this in the device tree?

After reading the following links:
https://lore.kernel.org/all/87fsw124wn.wl-kuninori.morimoto.gx@renesas.com/
https://lore.kernel.org/r/87ilbx1kh3.wl-kuninori.morimoto.gx@renesas.com
I found that this is a case of 1:N cpus to codecs, and this can be
solved using audio-graph-card2.
So I set up a device tree like this:
wm8782_1: stereo-adc-1 {
    	compatible = "wlf,wm8782";
    	Vdda-supply = <&reg_vcc>;
    	Vdd-supply = <&reg_vcc>;
    	#sound-dai-cells = <0>;
    	port {
    		wm8782_1_ep: endpoint {
    			remote-endpoint = <&card_ep_1>;
    		};
    	};
    };
wm8782_2: stereo-adc-2 {
    	compatible = "wlf,wm8782";
    	Vdda-supply = <&reg_vcc>;
    	Vdd-supply = <&reg_vcc>;
    	#sound-dai-cells = <0>;
    	port {
    		wm8782_2_ep: endpoint {
    			remote-endpoint = <&card_ep_2>;
    		};
    	};
    };
wm8782_3: stereo-adc-3 {
    	compatible = "wlf,wm8782";
    	Vdda-supply = <&reg_vcc>;
    	Vdd-supply = <&reg_vcc>;
    	#sound-dai-cells = <0>;
    	port {
    		wm8782_3_ep: endpoint {
    			remote-endpoint = <&card_ep_3>;
    		};
    	};
    };
sound {
    	compatible = "audio-graph-card2";
    	links = <&i2s2_port>;
    	multi {
    		ports {
    			#address-cells = <1>;
    			#size-cells = <0>;
    			port@0 {
    				card_ep_0: endpoint {
    					remote-endpoint = <&i2s2_ep>;
    				};
    			};
    			port@1 {
    				card_ep_1: endpoint {
    					remote-endpoint = <&wm8782_1_ep>;
    				};
    			};
    			port@2 {
    				card_ep_2: endpoint {
    					remote-endpoint = <&wm8782_2_ep>;
    				};
    			};
    			port@3 {
    				card_ep_3: endpoint {
    					remote-endpoint = <&wm8782_3_ep>;
    				};
    			};
    		};
    	};
    };
&i2s2 {
    	pinctrl-0 = <&i2s2_pins>, <&i2s2_din_pins>;
    	pinctrl-names = "default";
    	status = "okay";
    	i2s2_port: port {
    		format = "i2s";
    		mclk-fs = <128>;
    		bitclock-master;
    		frame-master;
    		i2s2_ep: endpoint {
    			remote-endpoint = <&card_ep_0>;
    		};
    	};
    };
Immediately I was able to record from the needed channels!
After tinkering with the driver registers I was even able to get it to
read the channels properly :)
I hope this helps somebody else in my situation.
John.