serial: stm32: add FIFO flush when port is closed

Transmission complete error is sent when ISR_TC is not set. If port closure is requested despite data in TDR / TX FIFO has not been sent (because of flow control), ISR_TC is not set and error message is sent on port closure but also when a new port is opened. Flush the data when port is closed, and send the transmission complete error message only when ISR_TC is not set and TDR / TX FIFO is not empty. Signed-off-by: Erwan Le Ray <[email protected]> Change-Id: I30c4cc1535d3a7bc1e8acd25b003f31fb555cd78 Reviewed-on: https://gerrit.st.com/c/mpu/oe/st/linux-stm32/+/181423 Reviewed-by: CITOOLS <[email protected]> Reviewed-by: CIBUILD <[email protected]> Reviewed-by: Fabrice GASNIER <[email protected]>
STMicroelectronics · Oct 20, 2020 · a56628a · a56628a
1 parent e5e4901
commit a56628a
Showing 1 changed file with 15 additions and 2 deletions.
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
@@ -903,9 +903,18 @@ static void stm32_usart_shutdown(struct uart_port *port)
 					 isr, (isr & USART_SR_TC),
 					 10, 100000);
 
-	if (ret)
+	/*
+	 * Send the TC error message only when ISR_TC is not set and
+	 * data stored in TDR / TX FIFO.
+	 */
+	if (ret && !(readl_relaxed(port->membase + ofs->isr) & USART_SR_TXE))
 		dev_err(port->dev, "transmission complete not set\n");
 
+	/* flush RX & TX FIFO */
+	if (ofs->rqr != UNDEF_REG)
+		stm32_usart_set_bits(port, ofs->rqr,
+				     USART_RQR_TXFRQ | USART_RQR_RXFRQ);
+
 	stm32_usart_clr_bits(port, ofs->cr1, val);
 
 	free_irq(port->irq, port);
@@ -968,7 +977,11 @@ static void stm32_usart_set_termios(struct uart_port *port,
 						(isr & USART_SR_TC),
 						10, 100000);
 
-	if (ret)
+	/*
+	 * Send the TC error message only when ISR_TC is not set and
+	 * data stored in TDR / TX FIFO.
+	 */
+	if (ret && !(readl_relaxed(port->membase + ofs->isr) & USART_SR_TXE))
 		dev_err(port->dev, "transmission complete not set\n");
 
 	/* Stop serial port and reset value */