linux-kernel - [PATCH 11/13] serial: stm32: add FIFO flush when port is closed

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Date:   Fri, 19 Feb 2021 18:47:34 +0100
From:   Erwan Le Ray <erwan.leray@...s.st.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>
CC:     <linux-serial@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        Erwan Le Ray <erwan.leray@...s.st.com>,
        Fabrice Gasnier <fabrice.gasnier@...s.st.com>,
        Valentin Caron <valentin.caron@...s.st.com>
Subject: [PATCH 11/13] 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, so the error isn't printed twice upon
next port opening.

Fixes: 64c32eab6603 ("serial: stm32: Add support of TC bit status check")
Signed-off-by: Erwan Le Ray <erwan.leray@...s.st.com>

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 45203648172b..dcc309fd5d2f 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -691,6 +691,11 @@ static void stm32_usart_shutdown(struct uart_port *port)
 	if (ret)
 		dev_err(port->dev, "Transmission is not complete\n");
 
+	/* flush RX & TX FIFO */
+	if (ofs->rqr != UNDEF_REG)
+		writel_relaxed(USART_RQR_TXFRQ | USART_RQR_RXFRQ,
+			       port->membase + ofs->rqr);
+
 	stm32_usart_clr_bits(port, ofs->cr1, val);
 
 	free_irq(port->irq, port);
-- 
2.17.1