Option to force X or Y to home first when homing the other axis

Marlin/Configuration_adv.h

@@ -362,6 +362,9 @@
 // When G28 is called, this option will make Y home before X
 //#define HOME_Y_BEFORE_X
 
+// Enable this if X or Y can't home without homing the other axis first.
+//#define CODEPENDENT_XY_HOMING
+
 // @section machine
 
 #define AXIS_RELATIVE_MODES {false, false, false, false}

Marlin/src/gcode/calibrate/G28.cpp

@@ -227,10 +227,14 @@ void GcodeSuite::G28(const bool always_home_all) {
 
     #endif
 
+    // Home Y (before X)
     #if ENABLED(HOME_Y_BEFORE_X)
 
-      // Home Y
-      if (home_all || homeY) {
+      if (home_all || homeY
+        #if ENABLED(CODEPENDENT_XY_HOMING)
+          || homeX
+        #endif
+      ) {
         HOMEAXIS(Y);
         #if ENABLED(DEBUG_LEVELING_FEATURE)
           if (DEBUGGING(LEVELING)) DEBUG_POS("> homeY", current_position);
@@ -240,7 +244,11 @@ void GcodeSuite::G28(const bool always_home_all) {
     #endif
 
     // Home X
-    if (home_all || homeX) {
+    if (home_all || homeX
+      #if ENABLED(CODEPENDENT_XY_HOMING) && DISABLED(HOME_Y_BEFORE_X)
+        || homeY
+      #endif
+    ) {
 
       #if ENABLED(DUAL_X_CARRIAGE)
 
@@ -271,8 +279,8 @@ void GcodeSuite::G28(const bool always_home_all) {
       #endif
     }
 
+    // Home Y (after X)
     #if DISABLED(HOME_Y_BEFORE_X)
-      // Home Y
       if (home_all || homeY) {
         HOMEAXIS(Y);
         #if ENABLED(DEBUG_LEVELING_FEATURE)

Marlin/src/inc/SanityCheck.h

@@ -886,12 +886,20 @@ static_assert(1 >= 0
 #endif
 
 /**
- * Homing Bump
+ * Homing
  */
 #if X_HOME_BUMP_MM < 0 || Y_HOME_BUMP_MM < 0 || Z_HOME_BUMP_MM < 0
   #error "[XYZ]_HOME_BUMP_MM must be greater than or equal to 0."
 #endif
 
+#if ENABLED(CODEPENDENT_XY_HOMING)
+  #if ENABLED(QUICK_HOME)
+    #error "QUICK_HOME is incompatible with CODEPENDENT_XY_HOMING."
+  #elif IS_KINEMATIC
+    #error "CODEPENDENT_XY_HOMING requires a Cartesian setup."
+  #endif
+#endif
+
 /**
  * Make sure Z_SAFE_HOMING point is reachable
  */