n3xx: Disable gpsdo reference source when enable_gps=0

When using enable_gps=0, the power to the LTE-Lite GPS chip is turned
off, and neither the reference sources (time/clock) nor the
location/time data (via gpsd) can be used.

This commit disables the gpsdo options for the set_time_source,
set_clock_source, and set_sync_source when enable_gps=0 is used, and
adds logging to inform the user about this.

This behaviour is consistent with X310, where `gpsdo` is only a valid
reference if the GPSDO module is plugged in.

The manual was also updated accordingly.

2 files changed, 26 insertions, 13 deletions

diff --git a/host/docs/usrp_n3xx.dox b/host/docs/usrp_n3xx.dox
index 477764e49..052f20ee9 100644
--- a/host/docs/usrp_n3xx.dox
+++ b/host/docs/usrp_n3xx.dox
@@ -643,7 +643,10 @@ will look like this:
 
 The N3xx series has an onboard GPSDO as well as a 25 MHz reference oscillator,
 which can both be used as time- and clock references. The GPSDO will function
-as a reference even when there is no GPS reception.
+as a reference even when there is no GPS reception. It can be powered off to
+reduce power usage and interference by supplying the `enable_gps=0` option in
+the configuration file (in this case, `gpsdo` cannot be used as a time or clock
+reference).
 
 Note that this does not enable the synchronization of multiple devices.
 Using an internal reference is the default.
@@ -662,6 +665,10 @@ auto usrp = uhd::usrp::multi_usrp::make(
     "type=n3xx,clock_source=external,time_source=external");
 ```
 
+
+Note: When disabling the GPS with `enable_gps=0` in the configuration file, or
+when manually launching MPM, the `gpsdo` reference source is not available.
+
 \subsection n3xx_synchronization_whiterabbit White Rabbit
 
 White Rabbit is an Ethernet-based synchronization procedure; it is an extension
diff --git a/mpm/python/usrp_mpm/periph_manager/n3xx.py b/mpm/python/usrp_mpm/periph_manager/n3xx.py
index 3eb9e709c..cdc58b8cc 100644
--- a/mpm/python/usrp_mpm/periph_manager/n3xx.py
+++ b/mpm/python/usrp_mpm/periph_manager/n3xx.py
@@ -228,13 +228,13 @@ class n3xx(ZynqComponents, PeriphManagerBase):
             self._gpios = TCA6424(int(self.mboard_info['rev']))
             self.log.trace("Enabling power of MGT156MHZ clk")
             self._gpios.set("PWREN-CLK-MGT156MHz")
+            self._gps_enabled = str2bool(
+                args.get('enable_gps', N3XX_DEFAULT_ENABLE_GPS))
+            if not self._gps_enabled:
+                self.log.info("Disabling GPS (gpsdo reference and time/location data).")
             self.enable_1g_ref_clock()
             self.enable_wr_ref_clock()
-            self.enable_gps(
-                enable=str2bool(
-                    args.get('enable_gps', N3XX_DEFAULT_ENABLE_GPS)
-                )
-            )
+            self.enable_gps(enable=self._gps_enabled)
             self.enable_fp_gpio(
                 enable=str2bool(
                     args.get(
@@ -573,8 +573,9 @@ class n3xx(ZynqComponents, PeriphManagerBase):
     ###########################################################################
     def get_clock_sources(self):
         " Lists all available clock sources. "
-        self.log.trace("Listing available clock sources...")
-        return ('external', 'internal', 'gpsdo')
+        if self._gps_enabled:
+            return 'external', 'internal', 'gpsdo'
+        return 'external', 'internal'
 
     def get_clock_source(self):
         " Returns the currently selected clock source "
@@ -600,7 +601,9 @@ class n3xx(ZynqComponents, PeriphManagerBase):
 
     def get_time_sources(self):
         " Returns list of valid time sources "
-        return ['internal', 'external', 'gpsdo', 'sfp0']
+        if self._gps_enabled:
+            return ['internal', 'external', 'gpsdo', 'sfp0']
+        return ['internal', 'external', 'sfp0']
 
     def get_time_source(self):
         " Return the currently selected time source "
@@ -630,13 +633,16 @@ class n3xx(ZynqComponents, PeriphManagerBase):
         Selects reference clock and PPS sources. Unconditionally re-applies the time
         source to ensure continuity between the reference clock and time rates.
         """
-
         clock_source = args.get('clock_source', self._clock_source)
-        assert clock_source in self.get_clock_sources()
+        assert clock_source in self.get_clock_sources(), \
+                "`{}' is not a valid clock source, valid choices are: {}".format(
+                    clock_source, ",".join(self.get_clock_sources()))
         time_source = args.get('time_source', self._time_source)
-        assert time_source in self.get_time_sources()
+        assert time_source in self.get_time_sources(), \
+                "`{}' is not a valid time source, valid choices are: {}".format(
+                    clock_source, ",".join(self.get_clock_sources()))
         if (clock_source == self._clock_source) and (time_source == self._time_source):
-            # Nothing change no need to do anything
+            # Nothing changed, no need to do anything
             self.log.trace("New sync source assignment matches"
                            "previous assignment. Ignoring update command.")
             return