Can the RX power be set to a value other than -15dBFS?
The documentation advises to set the RX power to -15 dBFS.
Are there any issues with setting it to -12 dBFS?
Yes is possible to support other RX power settings.
The -15dBFS is a conservative guideline because it is not always known if the user is going to be using a CFR when they start.
Typically with CFR the PAR of the waveform will be 6 to 8dB and the user can expect to need around 2dB for expansion.
This puts the PAR of the signal at the output of DPD around 10dB.
It is the users responsibility to understand their waveform and how much expansion they expect to require, (This will depend on how hard the PA is being driven etc.)
The RX power value can then be set based on this.
A higher value is better, in order to ensure that there is enough headroom to handle the expansion expected from the DPD.
Please see (Xilinx Answer 33521) for a detailed list of Digital Pre-Distortion (DPD) Reference Design Release Notes and Known Issues.