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drivers: flash: stm32h7x: use barriers to ensure the writes are flushed

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The STM32H7 flash driver read-back a register after writing it to ensure
it is flushed. This is very fragile and might break if a new compiler
version slightly reorder the instructions. Instead use a __DSB()
barrier like done on other STM32 SoC, which ensures that the registers
and the data writes are flushed at the compiler level, but also at the
Cortex-M7 level.

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
This commit is contained in:
Aurelien Jarno 2022-06-17 22:05:21 +02:00 • committed by Anas Nashif
commit c337b9f80b
1 changed files with 6 additions and 4 deletions
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10
drivers/flash/flash_stm32h7x.c
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@ -239,7 +239,6 @@ static struct flash_stm32_sector_t get_sector(const struct device *dev,
static int erase_sector(const struct device *dev, int offset)
{
int rc;
uint32_t tmp;
struct flash_stm32_sector_t sector = get_sector(dev, offset);
if (sector.bank == 0) {
@ -263,7 +262,7 @@ static int erase_sector(const struct device *dev, int offset)
| ((sector.sector_index << FLASH_CR_SNB_Pos) & FLASH_CR_SNB));
*(sector.cr) |= FLASH_CR_START;
/* flush the register write */
tmp = *(sector.cr);
__DSB();
rc = flash_stm32_wait_flash_idle(dev);
*(sector.cr) &= ~(FLASH_CR_SER | FLASH_CR_SNB);
@ -314,7 +313,6 @@ static int write_ndwords(const struct device *dev,
{
volatile uint64_t *flash = (uint64_t *)(offset
+ CONFIG_FLASH_BASE_ADDRESS);
uint32_t tmp;
int rc;
int i;
struct flash_stm32_sector_t sector = get_sector(dev, offset);
@ -346,11 +344,15 @@ static int write_ndwords(const struct device *dev,
*(sector.cr) |= FLASH_CR_PG;
/* Flush the register write */
tmp = *(sector.cr);
__DSB();
/* Perform the data write operation at the desired memory address */
for (i = 0; i < n; ++i) {
flash[i] = data[i];
/* Flush the data write */
__DSB();
wait_write_queue(dev, offset);
}