uhd: fixing TX DSP tuning on gen2 devices, special changes for n2xx

This fixes RX DSP core 200 from tuning outside range and causing overflows.

3 files changed, 55 insertions, 33 deletions

diff --git a/host/lib/usrp/cores/rx_dsp_core_200.cpp b/host/lib/usrp/cores/rx_dsp_core_200.cpp
index 2eafd6c59..160124b3e 100644
--- a/host/lib/usrp/cores/rx_dsp_core_200.cpp
+++ b/host/lib/usrp/cores/rx_dsp_core_200.cpp
@@ -25,6 +25,7 @@
 #include <boost/thread/thread.hpp> //thread sleep
 #include <boost/math/special_functions/round.hpp>
 #include <boost/math/special_functions/sign.hpp>
+#include <boost/numeric/conversion/bounds.hpp>
 #include <algorithm>
 #include <cmath>
 
@@ -228,14 +229,36 @@ public:
         if (std::abs(freq) > _tick_rate/2.0)
             freq -= boost::math::sign(freq)*_tick_rate;
 
-        //calculate the freq register word (signed)
+        //confirm that the target frequency is within range of the CORDIC
         UHD_ASSERT_THROW(std::abs(freq) <= _tick_rate/2.0);
+
+        /* Now calculate the frequency word. It is possible for this calculation
+         * to cause an overflow. As the requested DSP frequency approaches the
+         * master clock rate, that ratio multiplied by the scaling factor (2^32)
+         * will generally overflow within the last few kHz of tunable range.
+         * Thus, we check to see if the operation will overflow before doing it,
+         * and if it will, we set it to the integer min or max of this system.
+         */
+        boost::int32_t freq_word = 0;
+
         static const double scale_factor = std::pow(2.0, 32);
-        const boost::int32_t freq_word = boost::int32_t(boost::math::round((freq / _tick_rate) * scale_factor));
+        static const boost::int32_t int_max = boost::numeric::bounds<boost::int32_t>::highest();
+        static const boost::int32_t int_min = boost::numeric::bounds<boost::int32_t>::lowest();
+        if((freq / _tick_rate) >= (int_max / scale_factor)) {
+            /* Operation would have caused a positive overflow of int32. */
+            freq_word = boost::numeric::bounds<boost::int32_t>::highest();
+
+        } else if((freq / _tick_rate) <= (int_min / scale_factor)) {
+            /* Operation would have caused a negative overflow of int32. */
+            freq_word = boost::numeric::bounds<boost::int32_t>::lowest();
+
+        } else {
+            /* The operation is safe. Perform normally. */
+            freq_word = boost::int32_t(boost::math::round((freq / _tick_rate) * scale_factor));
+        }
 
-        //update the actual frequency
+        //program the frequency word into the device DSP
         const double actual_freq = (double(freq_word) / scale_factor) * _tick_rate;
-
         _iface->poke32(REG_DSP_RX_FREQ, boost::uint32_t(freq_word));
 
         return actual_freq;
diff --git a/host/lib/usrp/cores/tx_dsp_core_200.cpp b/host/lib/usrp/cores/tx_dsp_core_200.cpp
index 0e83a698b..3f397dd6a 100644
--- a/host/lib/usrp/cores/tx_dsp_core_200.cpp
+++ b/host/lib/usrp/cores/tx_dsp_core_200.cpp
@@ -169,14 +169,36 @@ public:
         if (std::abs(freq) > _tick_rate/2.0)
             freq -= boost::math::sign(freq)*_tick_rate;
 
-        //calculate the freq register word (signed)
+        //confirm that the target frequency is within range of the CORDIC
         UHD_ASSERT_THROW(std::abs(freq) <= _tick_rate/2.0);
+
+        /* Now calculate the frequency word. It is possible for this calculation
+         * to cause an overflow. As the requested DSP frequency approaches the
+         * master clock rate, that ratio multiplied by the scaling factor (2^32)
+         * will generally overflow within the last few kHz of tunable range.
+         * Thus, we check to see if the operation will overflow before doing it,
+         * and if it will, we set it to the integer min or max of this system.
+         */
+        boost::int32_t freq_word = 0;
+
         static const double scale_factor = std::pow(2.0, 32);
-        const boost::int32_t freq_word = boost::int32_t(boost::math::round((freq / _tick_rate) * scale_factor));
+        static const boost::int32_t int_max = boost::numeric::bounds<boost::int32_t>::highest();
+        static const boost::int32_t int_min = boost::numeric::bounds<boost::int32_t>::lowest();
+        if((freq / _tick_rate) >= (int_max / scale_factor)) {
+            /* Operation would have caused a positive overflow of int32. */
+            freq_word = boost::numeric::bounds<boost::int32_t>::highest();
+
+        } else if((freq / _tick_rate) <= (int_min / scale_factor)) {
+            /* Operation would have caused a negative overflow of int32. */
+            freq_word = boost::numeric::bounds<boost::int32_t>::lowest();
+
+        } else {
+            /* The operation is safe. Perform normally. */
+            freq_word = boost::int32_t(boost::math::round((freq / _tick_rate) * scale_factor));
+        }
 
-        //update the actual frequency
+        //program the frequency word into the device DSP
         const double actual_freq = (double(freq_word) / scale_factor) * _tick_rate;
-
         _iface->poke32(REG_DSP_TX_FREQ, boost::uint32_t(freq_word));
 
         return actual_freq;
diff --git a/host/lib/usrp/usrp2/usrp2_impl.cpp b/host/lib/usrp/usrp2/usrp2_impl.cpp
index 217c1d434..16e8a1f22 100644
--- a/host/lib/usrp/usrp2/usrp2_impl.cpp
+++ b/host/lib/usrp/usrp2/usrp2_impl.cpp
@@ -623,9 +623,9 @@ usrp2_impl::usrp2_impl(const device_addr_t &_device_addr){
             .coerce(boost::bind(&tx_dsp_core_200::set_host_rate, _mbc[mb].tx_dsp, _1))
             .subscribe(boost::bind(&usrp2_impl::update_tx_samp_rate, this, mb, 0, _1));
         _tree->create<double>(mb_path / "tx_dsps/0/freq/value")
-            .coerce(boost::bind(&usrp2_impl::set_tx_dsp_freq, this, mb, _1));
+            .coerce(boost::bind(&tx_dsp_core_200::set_freq, _mbc[mb].tx_dsp, _1));
         _tree->create<meta_range_t>(mb_path / "tx_dsps/0/freq/range")
-            .publish(boost::bind(&usrp2_impl::get_tx_dsp_freq_range, this, mb));
+            .publish(boost::bind(&tx_dsp_core_200::get_freq_range, _mbc[mb].tx_dsp));
 
         //setup dsp flow control
         const double ups_per_sec = device_args_i.cast<double>("ups_per_sec", 20);
@@ -809,29 +809,6 @@ void usrp2_impl::set_tx_fe_corrections(const std::string &mb, const double lo_fr
 #include <boost/math/special_functions/round.hpp>
 #include <boost/math/special_functions/sign.hpp>
 
-double usrp2_impl::set_tx_dsp_freq(const std::string &mb, const double freq_){
-    double new_freq = freq_;
-    const double tick_rate = _tree->access<double>("/mboards/"+mb+"/tick_rate").get();
-
-    //calculate the DAC shift (multiples of rate)
-    const int sign = boost::math::sign(new_freq);
-    const int zone = std::min(boost::math::iround(new_freq/tick_rate), 2);
-    const double dac_shift = sign*zone*tick_rate;
-    new_freq -= dac_shift; //update FPGA DSP target freq
-
-    //set the DAC shift (modulation mode)
-    if (zone == 0) _mbc[mb].codec->set_tx_mod_mode(0); //no shift
-    else _mbc[mb].codec->set_tx_mod_mode(sign*4/zone); //DAC interp = 4
-
-    return _mbc[mb].tx_dsp->set_freq(new_freq) + dac_shift; //actual freq
-}
-
-meta_range_t usrp2_impl::get_tx_dsp_freq_range(const std::string &mb){
-    const double tick_rate = _tree->access<double>("/mboards/"+mb+"/tick_rate").get();
-    const meta_range_t dsp_range = _mbc[mb].tx_dsp->get_freq_range();
-    return meta_range_t(dsp_range.start() - tick_rate*2, dsp_range.stop() + tick_rate*2, dsp_range.step());
-}
-
 void usrp2_impl::update_clock_source(const std::string &mb, const std::string &source){
     //NOTICE: U2_REG_MISC_CTRL_CLOCK is on the wb clock, and cannot be set from fifo_ctrl
     //clock source ref 10mhz