Watch idle() depth over 5

Marlin/src/MarlinCore.cpp

@@ -709,6 +709,10 @@ inline void manage_inactivity(const bool ignore_stepper_queue=false) {
  *  - Handle Joystick jogging
  */
 void idle(TERN_(ADVANCED_PAUSE_FEATURE, bool no_stepper_sleep/*=false*/)) {
+  #if ENABLED(MARLIN_DEV_MODE)
+    static uint8_t idle_depth = 0;
+    if (++idle_depth > 5) SERIAL_ECHOLNPAIR("idle() call depth: ", int(idle_depth));
+  #endif
 
   // Core Marlin activities
   manage_inactivity(TERN_(ADVANCED_PAUSE_FEATURE, no_stepper_sleep));
@@ -720,7 +724,7 @@ void idle(TERN_(ADVANCED_PAUSE_FEATURE, bool no_stepper_sleep/*=false*/)) {
   TERN_(MAX7219_DEBUG, max7219.idle_tasks());
 
   // Return if setup() isn't completed
-  if (marlin_state == MF_INITIALIZING) return;
+  if (marlin_state == MF_INITIALIZING) goto IDLE_DONE;
 
   // Handle filament runout sensors
   TERN_(HAS_FILAMENT_SENSOR, runout.run());
@@ -764,6 +768,7 @@ void idle(TERN_(ADVANCED_PAUSE_FEATURE, bool no_stepper_sleep/*=false*/)) {
 
   // Run i2c Position Encoders
   #if ENABLED(I2C_POSITION_ENCODERS)
+  {
     static millis_t i2cpem_next_update_ms;
     if (planner.has_blocks_queued()) {
       const millis_t ms = millis();
@@ -772,6 +777,7 @@ void idle(TERN_(ADVANCED_PAUSE_FEATURE, bool no_stepper_sleep/*=false*/)) {
         i2cpem_next_update_ms = ms + I2CPE_MIN_UPD_TIME_MS;
       }
     }
+  }
   #endif
 
   // Auto-report Temperatures / SD Status
@@ -793,6 +799,10 @@ void idle(TERN_(ADVANCED_PAUSE_FEATURE, bool no_stepper_sleep/*=false*/)) {
 
   // Update the LVGL interface
   TERN_(HAS_TFT_LVGL_UI, LV_TASK_HANDLER());
+
+  IDLE_DONE:
+  TERN_(MARLIN_DEV_MODE, idle_depth--);
+  return;
 }
 
 /**