⚡️ Reduce calls to set fan PWM (#23149)

Marlin/src/module/planner.cpp

@@ -1311,7 +1311,8 @@ void Planner::check_axes_activity() {
   #endif
 
   #if HAS_TAIL_FAN_SPEED
-    uint8_t tail_fan_speed[FAN_COUNT];
+    static uint8_t tail_fan_speed[FAN_COUNT];
+    bool fans_need_update = false;
   #endif
 
   #if ENABLED(BARICUDA)
@@ -1330,7 +1331,13 @@ void Planner::check_axes_activity() {
     #endif
 
     #if HAS_TAIL_FAN_SPEED
-      FANS_LOOP(i) tail_fan_speed[i] = thermalManager.scaledFanSpeed(i, block->fan_speed[i]);
+      FANS_LOOP(i) {
+        const uint8_t spd = thermalManager.scaledFanSpeed(i, block->fan_speed[i]);
+        if (tail_fan_speed[i] != spd) {
+          fans_need_update = true;
+          tail_fan_speed[i] = spd;
+        }
+      }
     #endif
 
     #if ENABLED(BARICUDA)
@@ -1358,7 +1365,13 @@ void Planner::check_axes_activity() {
     TERN_(HAS_CUTTER, cutter.refresh());
 
     #if HAS_TAIL_FAN_SPEED
-      FANS_LOOP(i) tail_fan_speed[i] = thermalManager.scaledFanSpeed(i);
+      FANS_LOOP(i) {
+        const uint8_t spd = thermalManager.scaledFanSpeed(i);
+        if (tail_fan_speed[i] != spd) {
+          fans_need_update = true;
+          tail_fan_speed[i] = spd;
+        }
+      }
     #endif
 
     #if ENABLED(BARICUDA)
@@ -1384,7 +1397,7 @@ void Planner::check_axes_activity() {
   // Update Fan speeds
   // Only if synchronous M106/M107 is disabled
   //
-  TERN_(HAS_TAIL_FAN_SPEED, sync_fan_speeds(tail_fan_speed));
+  TERN_(HAS_TAIL_FAN_SPEED, if (fans_need_update) sync_fan_speeds(tail_fan_speed));
 
   TERN_(AUTOTEMP, autotemp_task());