From 267beca895c7335cd03d586818ae07cf4acf6bb1 Mon Sep 17 00:00:00 2001
From: Quziwen <66210756+ItsGettingWorse@users.noreply.github.com>
Date: Sun, 24 Aug 2025 14:43:21 +0800
Subject: [PATCH] Update drv_usart.c

Fixed bugs under different optimization levels
---
 bsp/stm32/libraries/HAL_Drivers/drivers/drv_usart.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/bsp/stm32/libraries/HAL_Drivers/drivers/drv_usart.c b/bsp/stm32/libraries/HAL_Drivers/drivers/drv_usart.c
index 5174fbe769e..4a22585881e 100644
--- a/bsp/stm32/libraries/HAL_Drivers/drivers/drv_usart.c
+++ b/bsp/stm32/libraries/HAL_Drivers/drivers/drv_usart.c
@@ -11,6 +11,7 @@
  * 2020-05-02     whj4674672   support stm32h7 uart dma
  * 2020-09-09     forest-rain  support stm32wl uart
  * 2020-10-14     Dozingfiretruck   Porting for stm32wbxx
+ * 2025-08-24     ItsGettingWorse   Fixed bugs under different optimization levels
  */
 
 #include "board.h"
@@ -353,7 +354,10 @@ static int stm32_putc(struct rt_serial_device *serial, char c)
 #else
     uart->handle.Instance->DR = c;
 #endif
-    while (__HAL_UART_GET_FLAG(&(uart->handle), UART_FLAG_TC) == RESET && --block_timeout);
+    while (__HAL_UART_GET_FLAG(&(uart->handle), UART_FLAG_TC) == RESET && --block_timeout)
+    {
+        __DSB(); // Data Synchronization Barrier
+    }
     return (block_timeout != 0) ? 1 : -1;
 }