The axi-i2s.c driver currently only allows a ratio of 64 between the BCLK and LRCLK output frequencies, but it appears that it wasn't necessarily intended to always be that way. Near the top are the lines:
/* The frame size is configurable, but for now we always set it 64 bit */
#define AXI_I2S_BITS_PER_FRAME 64
Is there any intention to make this configurable?
If not, I would like to change this to be configurable - perhaps by a property in the DTS. If I do this, would ADI want to include this in its downloads and downstream linux source distributions?