Planner trapezoidal nominal_rate fix

Marlin/src/module/planner.cpp

@@ -730,8 +730,6 @@ void Planner::init() {
   #endif
 #endif
 
-#define MINIMAL_STEP_RATE 120
-
 /**
  * Get the current block for processing
  * and mark the block as busy.
@@ -800,6 +798,7 @@ void Planner::calculate_trapezoid_for_block(block_t * const block, const_float_t
   // Limit minimal step rate (Otherwise the timer will overflow.)
   NOLESS(initial_rate, uint32_t(MINIMAL_STEP_RATE));
   NOLESS(final_rate, uint32_t(MINIMAL_STEP_RATE));
+  NOLESS(block->nominal_rate, (uint32_t)MINIMAL_STEP_RATE);
 
   #if ANY(S_CURVE_ACCELERATION, LIN_ADVANCE)
     // If we have some plateau time, the cruise rate will be the nominal rate

Marlin/src/module/planner.h

@@ -267,6 +267,7 @@ typedef struct PlannerBlock {
              final_adv_steps;               // Advance steps for exit speed pressure
   #endif
 
+  #define MINIMAL_STEP_RATE _MAX((STEPPER_TIMER_RATE / HAL_TIMER_TYPE_MAX), 1)   // steps/s max. To prevent timer overflow, slowest is 1 step/s
   uint32_t nominal_rate,                    // The nominal step rate for this block in step_events/sec
            initial_rate,                    // The jerk-adjusted step rate at start of block
            final_rate,                      // The minimal rate at exit