RE: Request for help: How to upgrade a sound driver from kernel 4.14 to 6.6

[Steve Broshar <steve@xxxxxxxxxxxxxxxxxxxxxxxxx>]

Thanks for the help. I learned that to output I2S to a slave device, I shouldn't need a device-specific driver; that built-in drivers are all I need. I thought that was going to be easy to setup, but I have no luck with it. The boot log contains: platform sound-auditon: deferred probe pending

I have been working with chatgpt extensively as it seems you do too. It has a deep understanding of the linux kernel codebase. But, so far I cannot get the device to initialize (probe). Do you agree that I should be able to avoid the use of a device-specific driver? Do you see any issues in the device tree below?

Here's the device tree setup:

&sai2 {
	#sound-dai-cells = <0>;
	pinctrl-names = "default";
	pinctrl-0 = <&pinctrl_sai2>;
	assigned-clocks = <&clk IMX8MN_CLK_SAI2>;
	assigned-clock-parents = <&clk IMX8MN_AUDIO_PLL1_OUT>;
	assigned-clock-rates = <24576000>;
	fsl,sai-mclk-direction-output;
	status = "okay";
};

	pinctrl_sai2: sai2grp {
		fsl,pins = <
			MX8MN_IOMUXC_SAI2_TXC_SAI2_TX_BCLK      0xd6
			MX8MN_IOMUXC_SAI2_TXFS_SAI2_TX_SYNC     0xd6
			MX8MN_IOMUXC_SAI2_TXD0_SAI2_TX_DATA0    0xd6
			//MX8MN_IOMUXC_SAI2_RXD0_SAI2_RX_DATA0    0xd6
			MX8MN_IOMUXC_SAI2_MCLK_SAI2_MCLK    0xd6
		>;
	};


	// Compton audio output does not require a device-specific codec; the built-in, dummy driver is sufficient
	codec_auditon: codec-snd-doc-dummy {
		compatible = "linux,snd-soc-dummy";
	 	#sound-dai-cells = <0>;
	};

	// audio output for Compton can be accomplished via the built-in simple-audio-card driver
	// since only need to stream I2S; device (ADAU1467) does not require setup/control
	sound-auditon {
		// specify the built-in simple sound card driver
		compatible = "simple-audio-card";
		
		// description that shows in userland; i.e. via 'aplay -l'
		// auditon: a quantum of sound ;)
		simple-audio-card,name = "auditon";
		
		// specify stream format
		// supported options: i2s, right_j, left_j, dsp_a, dsp_b, ac97, pdm, msb, lsb
		//simple-audio-card,format = "i2s"; // with i2s, boot log shows: deferred probe pending and no device is setup
		simple-audio-card,format = "dsp_a";
		
		// assign CPU as master for bit-clock
		simple-audio-card,bitclock-master = <&cpu_link_auditon>;
		
		// assign CPU as master for frame-clock
		simple-audio-card,frame-master = <&cpu_link_auditon>;

		status = "okay";

		cpu_link_auditon: simple-audio-card,cpu {
			sound-dai = <&sai2>;
			dai-tdm-slot-num = <2>; // 2=>stereo
			dai-tdm-slot-width = <32>; // bits per slot
		};

		simple-audio-card,codec {
			sound-dai = <&codec_auditon>;
		};
	};

Thanks in advance.

Steve Broshar
Palmer Wireless Medtech
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