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Bit clock/Frame Sync enabled on i.MX7 at boot

Question asked by Fabio Antonini on May 21, 2019
Latest reply on May 24, 2019 by Fabio Antonini


I'm working on an i.MX7d custom board interfacing a Silicon Labs chipset on the SAI2 interface.

I have developed a machine driver to link che CPU dai (sai2) to the Silicon Labs chip codec modeled as a snd-soc-dummy codec. The sound card has been successfully configured and mapped from the operating system.

So I can successfully play an audio file to the chipset. I see the bitclock/framesync and data transmitted on the SAI2 inteface (by a probe) during the play of the audio file and hear the audio.

Anyway the Silicon Labs chipset requires that the Bit clock and frame sync should be provided since from the reset stage of the chip. So my question is how I can enable the bit clock and framesync on the SAI2 interface at boot stage even without any PCM streaming of audio data. Is it doable in any way (from kernel or u-boot)? In other words what i would like to do is to have bit clock and frame sync always enabled on the bus even when there is no streaming of data on the bus.

I have tried to enable the bitclock and frame sync from fsl_sai.c during the probe stage, but unsuccessfully. 

Every hints will be appreciated.

Thanks in advance