THERMAL_PROTECTION_GRACE_PERIOD is obsolete (#14798)

Marlin/src/HAL/HAL_LPC1768/HAL.h

 #define HAL_READ_ADC()         FilteredADC::get_result()
 #define HAL_ADC_READY()        FilteredADC::finished_conversion()
 
-// A grace period to allow ADC readings to stabilize, preventing false alarms
-#ifndef THERMAL_PROTECTION_GRACE_PERIOD
-  #define THERMAL_PROTECTION_GRACE_PERIOD 1000
-#endif
-
 // Parse a G-code word into a pin index
 int16_t PARSED_PIN_INDEX(const char code, const int16_t dval);
 // P0.6 thru P0.9 are for the onboard SD card

Marlin/src/Marlin.cpp

 
   for (;;) {
 
+    idle(); // Do an idle first so boot is slightly faster
+
     #if ENABLED(SDSUPPORT)
 
       card.checkautostart();
     if (queue.length < BUFSIZE) queue.get_available_commands();
     queue.advance();
     endstops.event_handler();
-    idle();
   }
 }

Marlin/src/module/temperature.cpp

   #endif
 #endif
 
-#ifndef THERMAL_PROTECTION_GRACE_PERIOD
-  #define THERMAL_PROTECTION_GRACE_PERIOD 0 // No grace period needed on well-behaved boards
-#endif
-
 Temperature thermalManager;
 
 /**
     millis_t ms = millis();
   #endif
 
-  #if HAS_THERMAL_PROTECTION
-    #if THERMAL_PROTECTION_GRACE_PERIOD > 0
-      static millis_t grace_period = ms + THERMAL_PROTECTION_GRACE_PERIOD;
-      if (ELAPSED(ms, grace_period)) grace_period = 0UL;
-    #else
-      static constexpr millis_t grace_period = 0UL;
-    #endif
-  #endif
-
   HOTEND_LOOP() {
     #if ENABLED(THERMAL_PROTECTION_HOTENDS)
-      if (!grace_period && degHotend(e) > temp_range[e].maxtemp)
+      if (degHotend(e) > temp_range[e].maxtemp)
         _temp_error((heater_ind_t)e, PSTR(MSG_T_THERMAL_RUNAWAY), TEMP_ERR_PSTR(MSG_THERMAL_RUNAWAY, e));
     #endif
 
   #if HAS_HEATED_BED
 
     #if ENABLED(THERMAL_PROTECTION_BED)
-      if (!grace_period && degBed() > BED_MAXTEMP)
+      if (degBed() > BED_MAXTEMP)
         _temp_error(H_BED, PSTR(MSG_T_THERMAL_RUNAWAY), TEMP_ERR_PSTR(MSG_THERMAL_RUNAWAY, H_BED));
     #endif
 
     #endif
 
     #if ENABLED(THERMAL_PROTECTION_CHAMBER)
-      if (!grace_period && degChamber() > CHAMBER_MAXTEMP)
+      if (degChamber() > CHAMBER_MAXTEMP)
         _temp_error(H_CHAMBER, PSTR(MSG_T_THERMAL_RUNAWAY), TEMP_ERR_PSTR(MSG_THERMAL_RUNAWAY, H_CHAMBER));
     #endif
 
 
 void Temperature::readings_ready() {
 
-  #if THERMAL_PROTECTION_GRACE_PERIOD > 0
-    const millis_t ms = millis();
-    static millis_t grace_period = ms + THERMAL_PROTECTION_GRACE_PERIOD; // NOTE: millis() == 0 on reset
-    if (ELAPSED(ms, grace_period)) grace_period = 0;
-  #else
-    static constexpr millis_t grace_period = 0;
-  #endif
-
   // Update the raw values if they've been read. Else we could be updating them during reading.
   if (!temp_meas_ready) set_current_temp_raw();
 
     temp_chamber.acc = 0;
   #endif
 
+  // Give ADC temperature readings time to settle at boot-up before testing
+  if (grace_period) return;
+
   static constexpr int8_t temp_dir[] = {
     #if ENABLED(HEATER_0_USES_MAX6675)
       0
     #endif // HOTENDS > 1
   };
 
-  // Give ADC temperature readings time to settle at boot-up before testing
-  if (grace_period) return;
-
   for (uint8_t e = 0; e < COUNT(temp_dir); e++) {
     const int8_t tdir = temp_dir[e];
     if (tdir) {