We've recently made our own board using the AD9361, Previously, we were working with the FMCOMMS2 and Zedboard. On our custom board, we use a 40MHz reference oscillator connected to pin XTAL_N (M12) and XTAL_P (M11) is left open per the AD9361 datasheet.
When porting our Zedboard software/firmware to our board, I forgot to set "adi,xo-disable-use-ext-refclk-enable" in the devicetree (as it was commented out for the Zedboard DTS). Thing is, even without xo-disable-use-ext-refclk-enable set, I could still configure the RFIC from Linux and get IQ data from the chip.
I rebuilt the devicetree with xo-disable-use-ext-refclk-enable set, and I'm actually seeing no difference in the behavior of the AD9361 (i.e. IQ looks the same).
So, what is "xo-disable-use-ext-refclk-enable" doing? The reason I ask is that we're seeing some spurs of the 40MHz clock and we're trying to hunt it down. The spurs of course could be a result of many things, but I'd still think xo-disable-use-ext-refclk-enable should have some effect on the IQ data we collect.
Edit: I should add that I'm using the AD Linux kernel from around the beginning of May. It's still Linux 3.13.