I had some time to gave it a try.
I checked out the kernel ( toradex_5.4-2.3.x-imx ) and set
CONFIG_SND_SOC_MAX98357A=y
This so it’s in the kernel and not a loadable module.
I used the exact device tree as supplied and aplay -l gives me the same result
~# aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: max98357a [max98357a], device 0: 30c30000.sai-HiFi HiFi-0 []
Subdevices: 1/1
Subdevice #0: subdevice #0
Sadly playing any audio gives a similar error as before.
I do not have the DAC hooked up to SAI3, but to SAI1 but as it’s a simple DAC with no feedback I think that should not be an issue and I should at least be able to play audio and see I2S data using a scope.
Could you tell me what version of the kernel and such you used, then we can try to recreate that on our side. Or perhaps for a test include the build kernel, module and dtb?
Best regards,
Rik