stm32/flash: Change flash_erase to only erase a single sector at a time.

An erase sector sits in a given flash bank and some MCUs have two flash
banks.  If trying to erase a range of sectors and that range crosses from
one flash bank into the next, the original implementation of
`flash_erase()` would not handle this case and would do the wrong thing.

This commit changes `flash_erase()` to only erase a single sector, which
sidesteps the need to handle flash-bank-crossing.  Most callers of this
function only need to erase a single sector anyway.

Signed-off-by: Damien George <damien@micropython.org>

ports/stm32/flash.c

@@ -272,11 +272,10 @@ int32_t flash_get_sector_info(uint32_t addr, uint32_t *start_addr, uint32_t *siz
     return -1;
 }
 
-int flash_erase(uint32_t flash_dest, uint32_t num_word32) {
-    // check there is something to write
-    if (num_word32 == 0) {
-        return 0;
-    }
+// Erase a single flash page which starts at the given address.
+// The address will be converted to a bank and sector number.
+int flash_erase(uint32_t flash_dest) {
+    const unsigned int num_sectors = 1;
 
     #if MICROPY_HW_STM32WB_FLASH_SYNCRONISATION
     // Acquire lock on the flash peripheral.
@@ -306,23 +305,23 @@ int flash_erase(uint32_t flash_dest, uint32_t num_word32) {
     __HAL_FLASH_CLEAR_FLAG(FLASH_FLAG_EOP | FLASH_FLAG_WRPERR | FLASH_FLAG_PGERR);
     EraseInitStruct.TypeErase = FLASH_TYPEERASE_PAGES;
     EraseInitStruct.PageAddress = flash_dest;
-    EraseInitStruct.NbPages = (4 * num_word32 + FLASH_PAGE_SIZE - 4) / FLASH_PAGE_SIZE;
+    EraseInitStruct.NbPages = num_sectors;
     #elif defined(STM32G0) || defined(STM32G4)
     __HAL_FLASH_CLEAR_FLAG(FLASH_FLAG_ALL_ERRORS);
     EraseInitStruct.TypeErase = FLASH_TYPEERASE_PAGES;
     EraseInitStruct.Page = get_page(flash_dest);
     EraseInitStruct.Banks = get_bank(flash_dest);
-    EraseInitStruct.NbPages = (4 * num_word32 + FLASH_PAGE_SIZE - 4) / FLASH_PAGE_SIZE;
+    EraseInitStruct.NbPages = num_sectors;
     #elif defined(STM32L0) || defined(STM32L1)
     __HAL_FLASH_CLEAR_FLAG(FLASH_FLAG_EOP | FLASH_FLAG_WRPERR | FLASH_FLAG_PGAERR);
     EraseInitStruct.TypeErase = FLASH_TYPEERASE_PAGES;
     EraseInitStruct.PageAddress = flash_dest;
-    EraseInitStruct.NbPages = (4 * num_word32 + FLASH_PAGE_SIZE - 4) / FLASH_PAGE_SIZE;
+    EraseInitStruct.NbPages = num_sectors;
     #elif (defined(STM32L4) && !defined(SYSCFG_MEMRMP_FB_MODE)) || defined(STM32WB) || defined(STM32WL)
     __HAL_FLASH_CLEAR_FLAG(FLASH_FLAG_ALL_ERRORS);
     EraseInitStruct.TypeErase = FLASH_TYPEERASE_PAGES;
     EraseInitStruct.Page = get_page(flash_dest);
-    EraseInitStruct.NbPages = (4 * num_word32 + FLASH_PAGE_SIZE - 4) / FLASH_PAGE_SIZE;
+    EraseInitStruct.NbPages = num_sectors;
     #elif defined(STM32L4)
     __HAL_FLASH_CLEAR_FLAG(FLASH_FLAG_ALL_ERRORS);
     // The sector returned by flash_get_sector_info can not be used
@@ -330,7 +329,7 @@ int flash_erase(uint32_t flash_dest, uint32_t num_word32) {
     EraseInitStruct.TypeErase = FLASH_TYPEERASE_PAGES;
     EraseInitStruct.Banks = get_bank(flash_dest);
     EraseInitStruct.Page = get_page(flash_dest);
-    EraseInitStruct.NbPages = get_page(flash_dest + 4 * num_word32 - 1) - EraseInitStruct.Page + 1;
+    EraseInitStruct.NbPages = num_sectors;
     #else
 
     #if defined(STM32H5)
@@ -354,7 +353,7 @@ int flash_erase(uint32_t flash_dest, uint32_t num_word32) {
     EraseInitStruct.Banks = get_bank(flash_dest);
     #endif
     EraseInitStruct.Sector = flash_get_sector_info(flash_dest, NULL, NULL);
-    EraseInitStruct.NbSectors = flash_get_sector_info(flash_dest + 4 * num_word32 - 1, NULL, NULL) - EraseInitStruct.Sector + 1;
+    EraseInitStruct.NbSectors = num_sectors;
     #if defined(STM32H5)
     EraseInitStruct.Sector &= 0x7f; // second bank should start counting at 0
     #endif

ports/stm32/flash.h

@@ -28,7 +28,7 @@
 
 bool flash_is_valid_addr(uint32_t addr);
 int32_t flash_get_sector_info(uint32_t addr, uint32_t *start_addr, uint32_t *size);
-int flash_erase(uint32_t flash_dest, uint32_t num_word32);
+int flash_erase(uint32_t flash_dest);
 int flash_write(uint32_t flash_dest, const uint32_t *src, uint32_t num_word32);
 
 #endif // MICROPY_INCLUDED_STM32_FLASH_H

ports/stm32/flashbdev.c

@@ -161,7 +161,7 @@ static void flash_bdev_irq_handler(void) {
 
     // This code erases the flash directly, waiting for it to finish
     if (!(flash_flags & FLASH_FLAG_ERASED)) {
-        flash_erase(flash_cache_sector_start, flash_cache_sector_size / 4);
+        flash_erase(flash_cache_sector_start);
         flash_flags |= FLASH_FLAG_ERASED;
         return;
     }

ports/stm32/mboot/main.c

@@ -465,7 +465,7 @@ static int mboot_flash_page_erase(uint32_t addr, uint32_t *next_addr) {
     }
 
     // Erase the flash page.
-    ret = flash_erase(sector_start, sector_size / sizeof(uint32_t));
+    ret = flash_erase(sector_start);
     if (ret != 0) {
         return ret;
     }