From: Sergey Organov <sorganov@gmail.com>
Date: Wed, 28 Aug 2019 21:37:51 +0300
Subject: serial: imx: get rid of unbounded busy-waiting loop
Git-commit: 2eda5345e4ef61b35101b4fef58417a41d8d53fd
Patch-mainline: v5.4-rc1
References: jsc#SLE-16106

imx_set_termios(): remove busy-waiting "drain Tx FIFO" loop. Worse
yet, it was potentially unbounded wait due to RTS/CTS (hardware)
handshake.

Let user space ensure draining is done before termios change, if
draining is needed in the first place.

Signed-off-by: Sergey Organov <sorganov@gmail.com>
Link: https://lore.kernel.org/r/1567017475-11919-2-git-send-email-sorganov@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
---
 drivers/tty/serial/imx.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index d9a73c7683ea..47b6156f5b2c 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -1644,7 +1644,7 @@ imx_uart_set_termios(struct uart_port *port, struct ktermios *termios,
 	uart_update_timeout(port, termios->c_cflag, baud);
 
 	/*
-	 * disable interrupts and drain transmitter
+	 * disable interrupts
 	 */
 	old_ucr1 = imx_uart_readl(sport, UCR1);
 	imx_uart_writel(sport,
@@ -1652,9 +1652,6 @@ imx_uart_set_termios(struct uart_port *port, struct ktermios *termios,
 			UCR1);
 	imx_uart_writel(sport, old_ucr2 & ~UCR2_ATEN, UCR2);
 
-	while (!(imx_uart_readl(sport, USR2) & USR2_TXDC))
-		barrier();
-
 	/* then, disable everything */
 	imx_uart_writel(sport, old_ucr2 & ~(UCR2_TXEN | UCR2_RXEN | UCR2_ATEN), UCR2);