feat(pps): preserve loop dynamics across nav periods

soc/software/gps_system/header/gps/gps_ip_defines.h

@@ -55,6 +55,7 @@
 			#endif
 			#define GPS_NAV_BITS_PER_WEEK       30240000u
 			#define GPS_NAV_SOLVE_PERIOD_MS     (GPS_NAV_SOLVE_TIMER_TICKS * GPS_NAV_SOLVE_TIMER_TICK_MS)
+			#define GPS_NAV_BITS_PER_SUBFRAME   300u
 			/* Keep integrity statistics active, but do not let leave-one-out FDE
 			 * replace the full-WLS position until the real measurement-noise model
 			 * is calibrated.  The live stationary test produced a 22.7% exclusion
@@ -83,6 +84,8 @@
 			#error "GPS_NAV_SOLVE_TIMER_TICKS must be non-zero"
 			#elif ((GPS_NAV_BITS_PER_WEEK % GPS_NAV_SOLVE_TIMER_TICKS) != 0u)
 			#error "GPS_NAV_SOLVE_TIMER_TICKS must divide 30240000 GPS navigation bits per week"
+			#elif ((GPS_NAV_BITS_PER_SUBFRAME % GPS_NAV_SOLVE_TIMER_TICKS) != 0u)
+			#error "GPS_NAV_SOLVE_TIMER_TICKS must divide the 300-bit LNAV subframe"
 			#endif
 			_Static_assert((GPS_NAV_ENABLE_FDE == 0u) || (GPS_NAV_ENABLE_FDE == 1u),
 			               "GPS_NAV_ENABLE_FDE must be zero or one");

soc/software/gps_system/header/gps/gps_pps_quality.h

@@ -2,6 +2,9 @@
 #define GPS_PPS_QUALITY_H
 
 #include <stdbool.h>
+#include <stdint.h>
+
+#define GPS_PPS_BASELINE_UPDATE_PERIOD_SEC 0.200
 
 typedef enum {
 	GPS_PPS_PROFILE_HOLDOVER = 0,
@@ -29,6 +32,8 @@ typedef struct {
 	gps_pps_profile_t profile;
 	gps_pps_profile_t candidate;
 	unsigned int candidate_updates;
+	unsigned int upgrade_updates;
+	unsigned int degrade_updates;
 } gps_pps_quality_selector_t;
 
 typedef struct {
@@ -43,13 +48,17 @@ typedef struct {
 } gps_pps_loop_profile_t;
 
 void gps_pps_quality_selector_init(gps_pps_quality_selector_t* selector);
+void gps_pps_quality_selector_init_period(
+	gps_pps_quality_selector_t* selector,
+	double update_period_sec);
 
 /*
  * Select a bounded loop profile from timing geometry, code/carrier quality
- * and integrity. Upgrades require sustained evidence and degradations require
- * three consecutive observations. A single rejected WLS epoch is skipped
- * without resetting the loop; sustained loss enters holdover, while the
- * independent reference watchdog remains the final stale-data guard.
+ * and integrity. Upgrades and degradations require sustained evidence; their
+ * update counts are scaled from the proven 200 ms timing when period-aware
+ * initialization is used. A single rejected WLS epoch is skipped without
+ * resetting the loop; sustained loss enters holdover, while the independent
+ * reference watchdog remains the final stale-data guard.
  */
 gps_pps_profile_t gps_pps_quality_selector_update(
 	gps_pps_quality_selector_t* selector,
@@ -57,6 +66,22 @@ gps_pps_profile_t gps_pps_quality_selector_update(
 	bool* profile_changed_out);
 
 gps_pps_loop_profile_t gps_pps_loop_profile(gps_pps_profile_t profile);
+gps_pps_loop_profile_t gps_pps_loop_profile_for_period(
+	gps_pps_profile_t profile,
+	double update_period_sec);
+
+/*
+ * Map the proven 200 ms discrete poles to another update period.  The pole
+ * exponentiation preserves the current loop's continuous-time settling and
+ * damping while returning exactly the legacy coefficients at 200 ms.
+ */
+bool gps_pps_loop_coefficients(
+	gps_pps_loop_profile_t parameters,
+	double update_period_sec,
+	double clock_frequency_hz,
+	int64_t* kp_q46_out,
+	int64_t* ki_q46_out,
+	uint32_t* max_slew_q32_out);
 const char* gps_pps_profile_name(gps_pps_profile_t profile);
 
 #endif

soc/software/gps_system/header/gps/gps_pps_time_filter.h

@@ -58,7 +58,9 @@ bool gps_pps_reference_bias_drift(
  * linear oscillator drift.  The Doppler WLS clock-drift state predicts the
  * bias at the new capture epoch; only the residual bias noise is low-passed.
  * If Doppler is temporarily unavailable, a bounded, slower finite-difference
- * drift estimate keeps the filter usable in the robust profile.
+ * drift estimate keeps the filter usable in the robust profile. All three
+ * baseline per-update gains are converted from the actual elapsed time, so
+ * changing the NAV solve period does not change their real-time poles.
  *
  * COARSE is returned during initial settling, a reference-datum change, or
  * after a gap too long for bounded Doppler prediction. The independent