Maxim MAX98357A audio DAC without using the PCM_DIN pin

max98357a-no-din-overlay.dts

// Overlay for Maxim MAX98357A audio DAC without using the PCM_DIN pin

// dtparams:
//     sdmode-pin - Specify GPIO pin to which SD_MODE is connected (default 20).

/dts-v1/;
/plugin/;

/ {
    compatible = "brcm,bcm2835";

    /* Enable I2S without PCM_DIN pin */
    fragment@0 {
        target = <&i2s>;
        frag0: __overlay__ {
            pinctrl-0 = <&i2s_pins_no_din>;
            status = "okay";
        };
    };

    /* Configure the PCM pins */
    fragment@1 {
        target = <&gpio>;
        __overlay__ {
            i2s_pins_no_din: i2s_pins_no_din {
                brcm,pins = <18 19 21>; /* PCM_CLK, PCM_FS, PCM_DOUT */
                brcm,function = <4 4 4>; /* ALT0: PCM */
            };
        };
    };

    /* DAC whose SD_MODE pin is managed by driver (via GPIO pin) */
    fragment@2 {
        target-path = "/";
        __overlay__ {
            max98357a_dac: max98357a {
                compatible = "maxim,max98357a";
                #sound-dai-cells = <0>;
                sdmode-gpios = <&gpio 20 0>;   /* 2nd word overwritten by sdmode-pin parameter */
                status = "okay";
            };
        };
    };

    /* Soundcard connecting I2S to DAC with SD_MODE */
    fragment@3 {
        target = <&sound>;
        __overlay__ {
            compatible = "simple-audio-card";
            simple-audio-card,format = "i2s";
            simple-audio-card,name = "MAX98357A";
            status = "okay";
            simple-audio-card,cpu {
                sound-dai = <&i2s>;
            };
            simple-audio-card,codec {
                sound-dai = <&max98357a_dac>;
            };
        };
    };

    __overrides__ {
        sdmode-pin = <&max98357a_dac>,"sdmode-gpios:4";
    };
};