Linux version 4.4.103, alsa version k4.4.103, aarch64 chip. Sound card "realtek,rt5640" with "asoc-simple-card" driver, manufactor specific I2S driver, and codec driver "rt5640" in rt5640.c.

      Hardware is ok because sound is working with xubuntu system, but is not working with debian system which is our target system. "asoc-simple-card" driver and I2S driver are the same between these two systems, while "aux-det-gpio" is added to debian system with its related function disabled(in order to pass compilation. We do not have this gpio in hardware). Rt5640.c is different with linux kernel rt5640.c in github but it is truly working in xubuntu system.

      I disabled pulseaudio in debian and used "aplay" to test sound. So i do not think it is a problem of rootfs.

      I checked these drivers and dts file is matching them.  Sound framework initialization  seems to be fine in "boot_log" in the attachment.

      I have searched a lot with google but can not find the reason. I suspect it is a problem of ALSA!

      Thanks for your help. Any solution or recommendation to debug the sound problem is highly appreciated.

      Best regard!