uart_stm32: Fix conflit between poll_out and irq API

A lock was added to manage situation where the API poll_out and irq API
are used in same time.

Signed-off-by: Julien D'ascenzio <julien.dascenzio@paratronic.fr>

drivers/serial/uart_stm32.c

@@ -473,13 +473,19 @@ static void uart_stm32_poll_out(const struct device *dev,
 					unsigned char c)
 {
 	USART_TypeDef *UartInstance = UART_STRUCT(dev);
+	struct uart_stm32_data *data = DEV_DATA(dev);
 
 	/* Wait for TXE flag to be raised */
-	while (!LL_USART_IsActiveFlag_TXE(UartInstance)) {
+	while (1) {
+		if (atomic_cas(&data->tx_lock, 0, 1)) {
+			if (LL_USART_IsActiveFlag_TXE(UartInstance)) {
+				break;
+			}
+			atomic_set(&data->tx_lock, 0);
+		}
 	}
 
 #ifdef CONFIG_PM
-	struct uart_stm32_data *data = DEV_DATA(dev);
 
 	if (!data->tx_poll_stream_on) {
 		data->tx_poll_stream_on = true;
@@ -497,6 +503,7 @@ static void uart_stm32_poll_out(const struct device *dev,
 #endif /* CONFIG_PM */
 
 	LL_USART_TransmitData8(UartInstance, (uint8_t)c);
+	atomic_set(&data->tx_lock, 0);
 }
 
 static int uart_stm32_err_check(const struct device *dev)
@@ -593,10 +600,12 @@ static int uart_stm32_fifo_read(const struct device *dev, uint8_t *rx_data,
 static void uart_stm32_irq_tx_enable(const struct device *dev)
 {
 	USART_TypeDef *UartInstance = UART_STRUCT(dev);
-
-#ifdef CONFIG_PM
 	struct uart_stm32_data *data = DEV_DATA(dev);
 
+	while (atomic_cas(&data->tx_lock, 0, 1) == false) {
+	}
+
+#ifdef CONFIG_PM
 	data->tx_poll_stream_on = false;
 	uart_stm32_pm_constraint_set(dev);
 #endif
@@ -606,9 +615,12 @@ static void uart_stm32_irq_tx_enable(const struct device *dev)
 static void uart_stm32_irq_tx_disable(const struct device *dev)
 {
 	USART_TypeDef *UartInstance = UART_STRUCT(dev);
+	struct uart_stm32_data *data = DEV_DATA(dev);
 
 	LL_USART_DisableIT_TC(UartInstance);
 
+	atomic_set(&data->tx_lock, 0);
+
 #ifdef CONFIG_PM
 	uart_stm32_pm_constraint_release(dev);
 #endif

drivers/serial/uart_stm32.h

@@ -58,6 +58,7 @@ struct uart_stm32_data {
 	uint32_t baud_rate;
 	/* clock device */
 	const struct device *clock;
+	atomic_t tx_lock;
 #ifdef CONFIG_UART_INTERRUPT_DRIVEN
 	uart_irq_callback_user_data_t user_cb;
 	void *user_data;