[MP1] Add pseudo-EEPROM support for RETRAM

Author: kbumsik

cores/arduino/stm32/stm32_eeprom.c

@@ -115,6 +115,8 @@ static inline uint32_t get_flash_end(void)
       defined(STM32WBxx)
 /* If FLASH_PAGE_NUMBER is defined by user, this is not really end of the flash */
 #define FLASH_END  ((uint32_t)(FLASH_BASE + (((FLASH_PAGE_NUMBER +1) * FLASH_PAGE_SIZE))-1))
+#elif defined(EEPROM_RETRAM_MODE)
+#define FLASH_END  ((uint32_t)(EEPROM_RETRAM_START_ADDRESS + EEPROM_RETRAM_MODE_SIZE -1))
 #endif
 #ifndef FLASH_END
 #error "FLASH_END could not be defined"
@@ -130,6 +132,8 @@ static inline uint32_t get_flash_end(void)
  */
 #if defined(STM32L0xx)
 #define FLASH_BASE_ADDRESS  ((uint32_t)(DATA_EEPROM_BASE))
+#elif defined(EEPROM_RETRAM_MODE)
+#define FLASH_BASE_ADDRESS  EEPROM_RETRAM_START_ADDRESS
 #else
 #define FLASH_BASE_ADDRESS  ((uint32_t)((FLASH_END + 1) - FLASH_PAGE_SIZE))
 #endif
@@ -194,6 +198,20 @@ void eeprom_buffer_fill(void)
   memcpy(eeprom_buffer, (uint8_t *)(FLASH_BASE_ADDRESS), E2END + 1);
 }
 
+#if defined(EEPROM_RETRAM_MODE)
+
+/**
+  * @brief  This function writes the buffer content into the flash
+  * @param  none
+  * @retval none
+  */
+void eeprom_buffer_flush(void)
+{
+  memcpy((uint8_t *)(FLASH_BASE_ADDRESS), eeprom_buffer, E2END + 1);
+}
+
+#else /* defined(EEPROM_RETRAM_MODE) */
+
 /**
   * @brief  This function writes the buffer content into the flash
   * @param  none
@@ -306,6 +324,8 @@ void eeprom_buffer_flush(void)
 #endif
 }
 
+#endif /* defined(EEPROM_RETRAM_MODE) */
+
 #ifdef __cplusplus
 }
 #endif

cores/arduino/stm32/stm32_eeprom.h

@@ -45,6 +45,31 @@ extern "C" {
 
 /* Exported types ------------------------------------------------------------*/
 /* Exported constants --------------------------------------------------------*/
+#if defined(STM32MP1xx)
+/* Note for STM32MP1xx devices:
+ * Those devices do not have non-volatile memory. The emulation is done
+ * in RETRAM. Therefore data will be preserved *only* when VBAT is supplied
+ * (e.g. A coin battery is connected to CN3 on STM32MP157A_DK1) and
+ * the coprocessor is waken up from STANBY mode.
+ * The data won't be preserved from cold boot, even if VBAT is connected.
+ * See: https://community.st.com/s/question/0D50X0000B44pHUSQY/doesnt-the-mcu-coprocessor-have-nonvolatile-memory
+ */
+#define EEPROM_RETRAM_MODE
+/* 4kB is the same size as EEPROM size of ATMega2560. */
+#ifndef EEPROM_RETRAM_MODE_SIZE
+#define EEPROM_RETRAM_MODE_SIZE ((uint32_t)(4*1024))
+#endif
+/* RETRAM start address is 0x00000000 (retset entry) and end address is
+ * 0x00020000 (64kB in total). The by default, ldscript.ld for STM32MP1xx
+ * does not define address between 0x00000298 (end of ISR Vector) and 0x00020000.
+ * So it is okay to use in this address range. Make sure ldscript.ld does not
+ * overrap the following address range.
+ */
+#ifndef EEPROM_RETRAM_START_ADDRESS
+#define EEPROM_RETRAM_START_ADDRESS (0x00000400UL)
+#endif
+#define E2END (EEPROM_RETRAM_MODE_SIZE - 1)
+#else
 #ifndef FLASH_PAGE_SIZE
 /*
  * FLASH_PAGE_SIZE is not defined for STM32F2xx, STM32F4xx and STM32F7xx
@@ -56,6 +81,7 @@ extern "C" {
 #define FLASH_PAGE_SIZE     ((uint32_t)(16*1024)) /* 16kB page */
 #endif
 #define E2END (FLASH_PAGE_SIZE - 1)
+#endif
 
 /* Exported macro ------------------------------------------------------------*/
 /* Exported functions ------------------------------------------------------- */