MPM: Init DSP only if there is a radio frontend

Users might build X400 bitfiles without RF blocks in it. In that
case the DSP info will report 0 for both the TX and RX.
MPM needs to handle that case correct an skip RF block initialization
an fall back to default values. This will allow bitfiles without
RF to load.

mpm/python/usrp_mpm/periph_manager/x4xx_clock_policy.py

@@ -229,6 +229,10 @@ def __init__(self, mboard_info, dboard_infos, args, log):
     def set_dsp_info(self, dsp_info):
         """Store the DSP info of the current FPGA image."""
         self._dsp_info = dsp_info
+        if self._dsp_info[0]["num_rx_chans"] == 0 and self._dsp_info[0]["num_tx_chans"] == 0:
+            return
+
+        # this part of DSP initialization is only relevant for radio frontends
         self._dsp_bw = dsp_info[0]["bw"]
         assert self._dsp_bw in [x[0] for x in self.master_to_sample_clk.values()]
 
@@ -406,6 +410,10 @@ def __init__(self, mboard_info, dboard_infos, args, log):
     def set_dsp_info(self, dsp_info):
         """Store the DSP info of the current FPGA image."""
         self._dsp_info = dsp_info
+        if self._dsp_info[0]["num_rx_chans"] == 0 and self._dsp_info[0]["num_tx_chans"] == 0:
+            return
+
+        # this part of DSP initialization is only relevant for radio frontends
         self._dsp_bw = dsp_info[0]["bw"]
         # We assume that SPC == the bitfile's spc_rx
         self._spc = dsp_info[0]["spc_rx"]