ADAU1761 Sound Card Initialized but No Audio on Playback

I'm working on a board using the ADAU1761 codec in I2S.  I'm trying to port the soundcard from Google's Coral EdgeTPU rt5645 codec on their dev board.  I am able to initialize the soundcard and link the adau-hifi dai.

**** List of PLAYBACK Hardware Devices ****

card 0: edgetpuaudiocar [edgetpu-audio-card], device 0: Coral Edge TPU HiFi adau-hifi-0 []

  Subdevices: 1/1

  Subdevice #0: subdevice #0

dmesg shows that the dai mapping is ok:

adau-hifi <-> 308b0000.sai mapping ok

the external MCLK source of the adau1761 is the 24.576Mhz 'mclk1' from the TPU in the DTS file:

&sai2 {
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_sai2>;
assigned-clocks =
<&clk IMX8MQ_CLK_SAI2>;
assigned-clock-parents = <&clk IMX8MQ_AUDIO_PLL1_OUT>;
assigned-clock-rates = <24576000>;
status = "okay";
clocks = <&clk IMX8MQ_CLK_SAI2_IPG>, <&clk IMX8MQ_CLK_DUMMY>,
<&clk IMX8MQ_CLK_SAI2_ROOT>, <&clk IMX8MQ_CLK_DUMMY>,
<&clk IMX8MQ_CLK_DUMMY>, <&clk IMX8MQ_AUDIO_PLL1_OUT>,
<&clk IMX8MQ_AUDIO_PLL2_OUT>;
clock-names = "bus", "mclk0", "mclk1", "mclk2", "mclk3", "pll8k", "pll11k";
};

where the specific clock powering the adau1761 is the set below in the DTS file:

&i2c3 {
	status = "okay";

        i2cmux4: i2cmux4@70 {
		compatible = "nxp,pca9546";
		reg = <0x70>;
		#address-cells = <1>;
		#size-cells = <0>;

		i2cm0: i2c@0 {
			#address-cells = <1>;
			#size-cells = <0>;
			reg = <0>;
			adau1761: adau1761@38 {
				compatible = "adi,adau1761";
				reg = <0x38>;
				clocks = <&clk IMX8MQ_CLK_SAI2_ROOT>;
				clock-names = "mclk1";

Machine Driver hw_params function contains the following clock settings:

/* set codec PLL source to the 24.576MHz (MCLK) platform clock */
ret = snd_soc_dai_set_pll(rtd->codec_dai, ADAU17X1_PLL, ADAU17X1_PLL_SRC_MCLK,
codec_clock, pll_rate);

ret = snd_soc_dai_set_sysclk(rtd->codec_dai, ADAU17X1_CLK_SRC_PLL, pll_rate,
SND_SOC_CLOCK_IN);

ret = snd_soc_dai_set_sysclk(rtd->cpu_dai, FSL_SAI_CLK_MAST1, codec_clock,
SND_SOC_CLOCK_OUT);

where 'codec_clock' is 24576000 and 'pll_rate' is 49152000

However, when I play sound on the device, I only hear silence from the speaker's output. I cannot even see waveforms from an oscilloscope probe on the LOUT and ROUT pins of the adau1761 device before they connect to the amplifier.  I am making sure that all settings in alsamixer are turned up.

If playing sound via aplay while specifying the playback device does not hang, does that mean that clocks /etc are set up correctly?

I am just trying to get basic functional playback and capture working on this device, so I am not using any "adau1761.bin" file.