fix: defer ch390 exti until rtos is ready

Core/Src/gpio.c

@@ -76,9 +76,15 @@ void MX_GPIO_Init(void)
   GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
   HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);
 
-  /* EXTI interrupt init*/
+  /* EXTI interrupt init
+   * Keep CH390 INT masked during early boot.  PB0 may already be asserted at
+   * power-on, while the FreeRTOS semaphore is not created until
+   * MX_FREERTOS_Init().  The network driver enables EXTI0 after CH390 and the
+   * RTOS objects are ready.
+   */
+  HAL_NVIC_DisableIRQ(EXTI0_IRQn);
+  __HAL_GPIO_EXTI_CLEAR_IT(GPIO_PIN_0);
   HAL_NVIC_SetPriority(EXTI0_IRQn, 6, 0);
-  HAL_NVIC_EnableIRQ(EXTI0_IRQn);
 
 }