We have a board with an adv7842 and an adau1701. The digital audio output pins from the adv7842 are routed to the adau1701's multipurpose pins, which are configured to receive I2S.
Originally, we had the adau1701 clocked off a crystal, and the adv7842's MCLK output pin floating. This did not work - we realized that BCLK and LRCLK need to be synchronous with MCLK. So we connected the adv7842's MCLK output to the adau1701's MCLK input and this works much better.
Now, my question is what is the best way to ensure that the adv7842 always clocks MCLKOUT? It seems that without choosing HDMI as the primary mode, it does not clock MCLKOUT. I need the adau1701 to run all the time, irrespective of the primary video mode.