Improve STM32F4 Flash Behavior (#17946)

Marlin/src/HAL/STM32/eeprom_flash.cpp

@@ -28,10 +28,13 @@
 
 #include "../shared/eeprom_api.h"
 
-
-// Only STM32F4 can support wear leveling at this time
-#ifndef STM32F4xx
-  #undef FLASH_EEPROM_LEVELING
+#if HAS_SERVOS
+  #include "Servo.h"
+  #define PAUSE_SERVO_OUTPUT() libServo::pause_all_servos()
+  #define RESUME_SERVO_OUTPUT() libServo::resume_all_servos()
+#else  
+  #define PAUSE_SERVO_OUTPUT()
+  #define RESUME_SERVO_OUTPUT()
 #endif
 
 /**
@@ -139,6 +142,11 @@ bool PersistentStore::access_start() {
 bool PersistentStore::access_finish() {
 
   if (eeprom_data_written) {
+    #ifdef STM32F4xx
+      // MCU may come up with flash error bits which prevent some flash operations.
+      // Clear flags prior to flash operations to prevent errors.
+      __HAL_FLASH_CLEAR_FLAG(FLASH_FLAG_OPERR | FLASH_FLAG_WRPERR | FLASH_FLAG_PGAERR | FLASH_FLAG_PGPERR | FLASH_FLAG_PGSERR);
+    #endif    
 
     #if ENABLED(FLASH_EEPROM_LEVELING)
 
@@ -159,7 +167,11 @@ bool PersistentStore::access_finish() {
         current_slot = EEPROM_SLOTS - 1;
         UNLOCK_FLASH();
 
+        PAUSE_SERVO_OUTPUT();
+        DISABLE_ISRS();
         status = HAL_FLASHEx_Erase(&EraseInitStruct, &SectorError);
+        ENABLE_ISRS();
+        RESUME_SERVO_OUTPUT();
         if (status != HAL_OK) {
           DEBUG_ECHOLNPAIR("HAL_FLASHEx_Erase=", status);
           DEBUG_ECHOLNPAIR("GetError=", HAL_FLASH_GetError());
@@ -204,7 +216,18 @@ bool PersistentStore::access_finish() {
       return success;
 
     #else
+      // The following was written for the STM32F4 but may work with other MCUs as well.
+      // Most STM32F4 flash does not allow reading from flash during erase operations.
+      // This takes about a second on a STM32F407 with a 128kB sector used as EEPROM.
+      // Interrupts during this time can have unpredictable results, such as killing Servo
+      // output. Servo output still glitches with interrupts disabled, but recovers after the
+      // erase.
+      PAUSE_SERVO_OUTPUT();
+      DISABLE_ISRS();
       eeprom_buffer_flush();
+      ENABLE_ISRS();
+      RESUME_SERVO_OUTPUT();
+
       eeprom_data_written = false;
     #endif
   }