STM32 timer simplification (#11995)

Prescalers aren't calculated for the given target frequency.
Stepper timer should run at 2 Mhz and temperature timer at 72 Khz.

Marlin/src/HAL/HAL_STM32/HAL_timers_STM32.cpp

 void HAL_timer_start(const uint8_t timer_num, const uint32_t frequency) {
 
   if (!timers_initialised[timer_num]) {
-    constexpr uint32_t step_prescaler = STEPPER_TIMER_PRESCALE - 1,
+    uint32_t step_prescaler = STEPPER_TIMER_PRESCALE - 1,
                        temp_prescaler = TEMP_TIMER_PRESCALE - 1;
     switch (timer_num) {
       case STEP_TIMER_NUM:

Marlin/src/HAL/HAL_STM32/HAL_timers_STM32.h

 
 #define FORCE_INLINE __attribute__((always_inline)) inline
 
-#define hal_timer_t uint32_t  // TODO: One is 16-bit, one 32-bit - does this need to be checked?
+#define hal_timer_t uint32_t
 #define HAL_TIMER_TYPE_MAX 0xFFFF
 
 #ifdef STM32F0xx
 
-  #define HAL_TIMER_RATE         (HAL_RCC_GetSysClockFreq())  // frequency of timer peripherals
-  #define TEMP_TIMER_PRESCALE    666  // prescaler for setting temperature timer, 72Khz
-  #define STEPPER_TIMER_PRESCALE 24   // prescaler for setting stepper timer, 2Mhz
+  #define HAL_TIMER_RATE (HAL_RCC_GetSysClockFreq()) // frequency of timer peripherals
 
   #define STEP_TIMER 16
   #define TEMP_TIMER 17
 
 #elif defined STM32F1xx
 
-  #define HAL_TIMER_RATE         (HAL_RCC_GetPCLK2Freq())  // frequency of timer peripherals
-  #define TEMP_TIMER_PRESCALE    1000 // prescaler for setting temperature timer, 72Khz
-  #define STEPPER_TIMER_PRESCALE 36   // prescaler for setting stepper timer, 2Mhz.
+  #define HAL_TIMER_RATE (HAL_RCC_GetPCLK2Freq()) // frequency of timer peripherals
 
   #define STEP_TIMER 4
   #define TEMP_TIMER 2
 
 #elif defined STM32F4xx
 
-  #define HAL_TIMER_RATE         (HAL_RCC_GetPCLK2Freq())  // frequency of timer peripherals
-  #define TEMP_TIMER_PRESCALE    2333 // prescaler for setting temperature timer, 72Khz
-  #define STEPPER_TIMER_PRESCALE 84   // prescaler for setting stepper timer, 2Mhz
+  #define HAL_TIMER_RATE (HAL_RCC_GetPCLK2Freq()) // frequency of timer peripherals
 
   #define STEP_TIMER 4
   #define TEMP_TIMER 5
 
 #elif defined STM32F7xx
 
-  #define HAL_TIMER_RATE         (HAL_RCC_GetSysClockFreq()/2)  // frequency of timer peripherals
-  #define TEMP_TIMER_PRESCALE    1500 // prescaler for setting temperature timer, 72Khz
-  #define STEPPER_TIMER_PRESCALE 54   // prescaler for setting stepper timer, 2Mhz.
+  #define HAL_TIMER_RATE (HAL_RCC_GetSysClockFreq()/2) // frequency of timer peripherals
 
   #define STEP_TIMER 5
   #define TEMP_TIMER 7
 #define TEMP_TIMER_NUM 1  // index of timer to use for temperature
 #define PULSE_TIMER_NUM STEP_TIMER_NUM
 
-#define STEPPER_TIMER_RATE     (HAL_TIMER_RATE / STEPPER_TIMER_PRESCALE)   // frequency of stepper timer
-#define STEPPER_TIMER_TICKS_PER_US ((STEPPER_TIMER_RATE) / 1000000) // stepper timer ticks per µs
+#define TEMP_TIMER_RATE 72000 // 72 Khz
+#define TEMP_TIMER_PRESCALE ((HAL_TIMER_RATE)/(TEMP_TIMER_RATE))
+#define TEMP_TIMER_FREQUENCY 1000
 
-#define TEMP_TIMER_FREQUENCY  1000  // temperature interrupt frequency
+#define STEPPER_TIMER_RATE 2000000 // 2 Mhz
+#define STEPPER_TIMER_PRESCALE ((HAL_TIMER_RATE)/(STEPPER_TIMER_RATE))
+#define STEPPER_TIMER_TICKS_PER_US ((STEPPER_TIMER_RATE) / 1000000) // stepper timer ticks per µs
 
-#define PULSE_TIMER_RATE       STEPPER_TIMER_RATE   // frequency of pulse timer
-#define PULSE_TIMER_PRESCALE   STEPPER_TIMER_PRESCALE
+#define PULSE_TIMER_RATE STEPPER_TIMER_RATE
+#define PULSE_TIMER_PRESCALE STEPPER_TIMER_PRESCALE
 #define PULSE_TIMER_TICKS_PER_US STEPPER_TIMER_TICKS_PER_US
 
 #define __TIMER_DEV(X) TIM##X