I am working with the imx8mp processor, receiving serial data over SAI2. The SAI's VERID register indicates version 3.1 with timestamp registers. I have the SAI2 receive working and dumping the incoming data into a DMA buffer. The master clock, bit clock, and frame clock are all generated externally. I expected to get values in the timestamp counter (RTSR), bit counter (RBCR), and bit timestamp (RBCTR), but they stay at zero even as I am receiving valid data. I have verified via readback that the receive timestamp control (RTCR) is 0x000003, which should allow the timestamp counter to increment even without the bit counter incrementing. Is there anything else I need to configure to get the bit counter and timestamp working?
