n320: fix issue that occasionally prevents lo_locked upon first set_freq

For certain frequencies, the LMX2592 will sporadically fail to lock upon
the very first tune. When this happens, subsequent tunes (even to the same
frequency) do lock. This issue seems to be resolved by programming the FCAL
adjustment register fields (FCAL_LPFD_ADJ/FCAL_HPFD_ADJ) as described in
the LMX2592 datasheet. These fields adjust the FCAL calibration speed to
better accomodate PFD frequencies below 20MHz or above 100MHz.

This patch also fixes a few name typos in the register map that were
directly in the scope of this change.

1 files changed, 43 insertions, 6 deletions

diff --git a/host/lib/usrp/common/lmx2592.cpp b/host/lib/usrp/common/lmx2592.cpp
index 0833bc7c4..0a409f117 100644
--- a/host/lib/usrp/common/lmx2592.cpp
+++ b/host/lib/usrp/common/lmx2592.cpp
@@ -235,6 +235,8 @@ public:
             pfd_freq = input_freq / _regs.pll_r;
         }
 
+        _set_fcal_adj_values(pfd_freq);
+
         // Calculate N and frac
         const auto N_dot_F = target_vco_freq / (pfd_freq * prescaler);
         auto N             = static_cast<uint16_t>(std::floor(N_dot_F));
@@ -253,12 +255,12 @@ public:
         // Calculate Fnum
         const auto initial_fnum = static_cast<uint32_t>(std::round(frac * fden));
         const auto fnum         = (spur_dodging) ? _find_fnum(N,
-                                               initial_fnum,
-                                               fden,
-                                               prescaler,
-                                               pfd_freq,
-                                               output_divider,
-                                               spur_dodging_threshold)
+                              initial_fnum,
+                              fden,
+                              prescaler,
+                              pfd_freq,
+                              output_divider,
+                              spur_dodging_threshold)
                                          : initial_fnum;
 
         // Calculate mash_seed
@@ -519,6 +521,41 @@ private: // Members
         }
     }
 
+    void _set_fcal_adj_values(const double pfd_freq)
+    {
+        // Adjust FCAL speed for particularly high or low PFD frequencies
+        if (pfd_freq < 5e6) {
+            _regs.fcal_lpfd_adj = lmx2592_regs_t::fcal_lpfd_adj_t::FCAL_LPFD_ADJ_5MHZ;
+            _regs.fcal_hpfd_adj = lmx2592_regs_t::fcal_hpfd_adj_t::FCAL_HPFD_ADJ_UNUSED;
+            _regs.pfd_ctl       = lmx2592_regs_t::pfd_ctl_t::PFD_CTL_DUAL_PFD;
+        } else if (pfd_freq < 10e6) {
+            _regs.fcal_lpfd_adj = lmx2592_regs_t::fcal_lpfd_adj_t::FCAL_LPFD_ADJ_10MHZ;
+            _regs.fcal_hpfd_adj = lmx2592_regs_t::fcal_hpfd_adj_t::FCAL_HPFD_ADJ_UNUSED;
+            _regs.pfd_ctl       = lmx2592_regs_t::pfd_ctl_t::PFD_CTL_DUAL_PFD;
+        } else if (pfd_freq < 20e6) {
+            _regs.fcal_lpfd_adj = lmx2592_regs_t::fcal_lpfd_adj_t::FCAL_LPFD_ADJ_20MHZ;
+            _regs.fcal_hpfd_adj = lmx2592_regs_t::fcal_hpfd_adj_t::FCAL_HPFD_ADJ_UNUSED;
+            _regs.pfd_ctl       = lmx2592_regs_t::pfd_ctl_t::PFD_CTL_DUAL_PFD;
+        } else if (pfd_freq <= 100e6) {
+            _regs.fcal_lpfd_adj = lmx2592_regs_t::fcal_lpfd_adj_t::FCAL_LPFD_ADJ_UNUSED;
+            _regs.fcal_hpfd_adj = lmx2592_regs_t::fcal_hpfd_adj_t::FCAL_HPFD_ADJ_UNUSED;
+            _regs.pfd_ctl       = lmx2592_regs_t::pfd_ctl_t::PFD_CTL_DUAL_PFD;
+        } else if (pfd_freq <= 150e6) {
+            _regs.fcal_lpfd_adj = lmx2592_regs_t::fcal_lpfd_adj_t::FCAL_LPFD_ADJ_UNUSED;
+            _regs.fcal_hpfd_adj = lmx2592_regs_t::fcal_hpfd_adj_t::FCAL_HPFD_ADJ_100MHZ;
+            _regs.pfd_ctl       = lmx2592_regs_t::pfd_ctl_t::PFD_CTL_DUAL_PFD;
+        } else if (pfd_freq <= 200e6) {
+            _regs.fcal_lpfd_adj = lmx2592_regs_t::fcal_lpfd_adj_t::FCAL_LPFD_ADJ_UNUSED;
+            _regs.fcal_hpfd_adj = lmx2592_regs_t::fcal_hpfd_adj_t::FCAL_HPFD_ADJ_150MHZ;
+            _regs.pfd_ctl       = lmx2592_regs_t::pfd_ctl_t::PFD_CTL_DUAL_PFD;
+        } else {
+            // Note, this case requires single-loop PFD which increases PLL noise floor
+            _regs.fcal_lpfd_adj = lmx2592_regs_t::fcal_lpfd_adj_t::FCAL_LPFD_ADJ_UNUSED;
+            _regs.fcal_hpfd_adj = lmx2592_regs_t::fcal_hpfd_adj_t::FCAL_HPFD_ADJ_200MHZ;
+            _regs.pfd_ctl       = lmx2592_regs_t::pfd_ctl_t::PFD_CTL_SINGLE_PFD;
+        }
+    }
+
     // "k" is a derived value that indicates where sub-fractional spurs will be present
     // at a given Fden value.  A "k" value of 1 indicates there will be no spurs.
     // See the LMX2592 datasheet for more information