linux-kernel - [PATCH V2] tty: serial: lpuart: disable flow control while waiting for the transmit engine to complete

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Date:   Thu,  4 Aug 2022 15:04:20 +0800
From:   Sherry Sun <sherry.sun@....com>
To:     gregkh@...uxfoundation.org, jirislaby@...nel.org
Cc:     linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-imx@....com
Subject: [PATCH V2] tty: serial: lpuart: disable flow control while waiting for the transmit engine to complete

When the user initializes the uart port, and waits for the transmit
engine to complete in lpuart32_set_termios(), if the UART TX fifo has
dirty data and the UARTMODIR enable the flow control, the TX fifo may
never be empty. So here we should disable the flow control first to make
sure the transmit engin can complete.

Signed-off-by: Sherry Sun <sherry.sun@....com>
---
Changes in V2:
1. Rephrase the commit log as suggested by Jiri.
---
 drivers/tty/serial/fsl_lpuart.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index fc7d235a1e27..f0fccd2ff7ac 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -2172,6 +2172,7 @@ lpuart32_set_termios(struct uart_port *port, struct ktermios *termios,
 	uart_update_timeout(port, termios->c_cflag, baud);
 
 	/* wait transmit engin complete */
+	lpuart32_write(&sport->port, 0, UARTMODIR);
 	lpuart32_wait_bit_set(&sport->port, UARTSTAT, UARTSTAT_TC);
 
 	/* disable transmit and receive */
-- 
2.17.1