🧑‍💻 Define, apply F_CPU on HC32 (#27086)

Co-authored-by: Scott Lahteine <thinkyhead@users.noreply.github.com>

Marlin/src/HAL/HC32/app_config.h

@@ -64,7 +64,12 @@
 // redirect printf to host serial
 #define REDIRECT_PRINTF_TO_SERIAL 1
 
-// FIXME override F_CPU to PCLK1, as marlin freaks out otherwise
-#define F_CPU (SYSTEM_CLOCK_FREQUENCIES.pclk1)
+// F_CPU must be known at compile time, but on HC32F460 it's not.
+// Thus we assume HCLK to be 200MHz, as that's what is configured in 
+// 'core_hook_sysclock_init' in 'sysclock.cpp'.
+// If you face issues with this assumption, please double-check with the values
+// printed by 'MarlinHAL::HAL_clock_frequencies_dump'.
+// see also: HAL_TIMER_RATE in timers.h
+#define F_CPU 200000000 // 200MHz HCLK
 
 #endif // _HC32_APP_CONFIG_H_

Marlin/src/HAL/HC32/sysclock.cpp

@@ -96,8 +96,8 @@ void core_hook_sysclock_init() {
     #endif
   #endif
 
-  // sysclk is now configured to 200 MHz PLL output
-  constexpr uint32_t sysclock = 200000000;
+  // sysclk is now configured according to F_CPU (i.e., 200MHz PLL output)
+  constexpr uint32_t sysclock = F_CPU;
 
   // Setup clock divisors for sysclk = 200 MHz
   // Note: PCLK1 is used for step+temp timers, and need to be kept at 50 MHz (until there is a better solution)

Marlin/src/HAL/HC32/timers.h

@@ -38,44 +38,48 @@ extern Timer0 step_timer;
 // Timer Configurations
 //
 
-// TODO: some calculations (step irq min_step_rate) require the timer rate to be known at compile time
-//       this is not possible with the HC32F460, as the timer rate depends on PCLK1
-//       as a workaround, PCLK1 = 50MHz is assumed (check with clock dump in MarlinHAL::init())
-#define HAL_TIMER_RATE 50000000 // 50MHz
-// #define HAL_TIMER_RATE TIMER0_BASE_FREQUENCY
-
-// TODO: CYCLES_PER_MICROSECOND seems to be used by Marlin to calculate the number of cycles per microsecond in the timer ISRs
-//       by default, it uses F_CPU, but since that is not known at compile time for HC32, we overwrite it here
-#undef CYCLES_PER_MICROSECOND
-#define CYCLES_PER_MICROSECOND (HAL_TIMER_RATE / 1000000UL)
+/**
+ * HAL_TIMER_RATE must be known at compile time since it's used to calculate
+ * STEPPER_TIMER_RATE, which is used in 'constexpr' calculations.
+ * On the HC32F460 the timer rate depends on PCLK1, which is derived from the
+ * system clock configured at runtime. As a workaround, we use the existing
+ * assumption of a 200MHz clock, defining F_CPU as 200000000, then configure PCLK1
+ * as F_CPU with a divider of 4 in 'sysclock.cpp::core_hook_sysclock_init'.
+ *
+ * If you face issues with this assumption, please double-check with the values
+ * printed by 'MarlinHAL::HAL_clock_frequencies_dump'.
+ *
+ * TODO: If the 'constexpr' requirement is ever lifted, use TIMER0_BASE_FREQUENCY instead
+ */
+#define HAL_TIMER_RATE (F_CPU / 4) // i.e., 50MHz
+//#define HAL_TIMER_RATE TIMER0_BASE_FREQUENCY
 
 // Temperature timer
-#define TEMP_TIMER_NUM (&temp_timer)
-#define TEMP_TIMER_PRIORITY DDL_IRQ_PRIORITY_02
-#define TEMP_TIMER_PRESCALE 16ul
-#define TEMP_TIMER_RATE 1000                 // 1kHz
-#define TEMP_TIMER_FREQUENCY TEMP_TIMER_RATE // Alias for Marlin
+#define TEMP_TIMER_NUM        (&temp_timer)
+#define TEMP_TIMER_PRIORITY   DDL_IRQ_PRIORITY_02
+#define TEMP_TIMER_PRESCALE     16UL          // 12.5MHz
+#define TEMP_TIMER_RATE       1000            // 1kHz
+#define TEMP_TIMER_FREQUENCY  TEMP_TIMER_RATE // 1kHz also
 
 // Stepper timer
-#define STEP_TIMER_NUM (&step_timer)
-#define STEP_TIMER_PRIORITY DDL_IRQ_PRIORITY_01
-#define STEPPER_TIMER_PRESCALE 16ul
+#define STEP_TIMER_NUM         (&step_timer)
+#define STEP_TIMER_PRIORITY    DDL_IRQ_PRIORITY_00  // Top priority, nothing else uses it
+#define STEPPER_TIMER_PRESCALE  16UL                // 12.5MHz
 
-// TODO: STEPPER_TIMER_RATE seems to work fine like this, but requires further testing...
-#define STEPPER_TIMER_RATE (HAL_TIMER_RATE / STEPPER_TIMER_PRESCALE) // 50MHz / 16 = 3.125MHz
-#define STEPPER_TIMER_TICKS_PER_US (STEPPER_TIMER_RATE / 1000000)
+#define STEPPER_TIMER_RATE (HAL_TIMER_RATE / STEPPER_TIMER_PRESCALE)  // 50MHz / 16 = 3.125MHz
+#define STEPPER_TIMER_TICKS_PER_US (STEPPER_TIMER_RATE / 1000000UL)   // Integer 3
 
 // Pulse timer (== stepper timer)
-#define PULSE_TIMER_NUM STEP_TIMER_NUM
-#define PULSE_TIMER_PRESCALE STEPPER_TIMER_PRESCALE
-#define PULSE_TIMER_TICKS_PER_US STEPPER_TIMER_TICKS_PER_US
+#define PULSE_TIMER_NUM           STEP_TIMER_NUM
+#define PULSE_TIMER_PRESCALE      STEPPER_TIMER_PRESCALE
+#define PULSE_TIMER_TICKS_PER_US  STEPPER_TIMER_TICKS_PER_US
 
 //
 // Channel aliases
 //
-#define MF_TIMER_TEMP TEMP_TIMER_NUM
-#define MF_TIMER_STEP STEP_TIMER_NUM
-#define MF_TIMER_PULSE PULSE_TIMER_NUM
+#define MF_TIMER_TEMP   TEMP_TIMER_NUM
+#define MF_TIMER_STEP   STEP_TIMER_NUM
+#define MF_TIMER_PULSE  PULSE_TIMER_NUM
 
 //
 // HAL functions

Marlin/src/inc/Warnings.cpp

@@ -864,3 +864,10 @@
 #if DISABLED(EDITABLE_STEPS_PER_UNIT)
   #warning "EDITABLE_STEPS_PER_UNIT is required to enable G92 runtime configuration of steps-per-unit."
 #endif
+
+/**
+ * HC32 clock speed is hard-coded in Marlin
+ */
+#if defined(ARDUINO_ARCH_HC32) && F_CPU == 200000000
+  #warning "HC32 clock is assumed to be 200MHz. If this isn't the case for your board please submit a report so we can add support."
+#endif