serial: imx: get rid of unbounded busy-waiting loop

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>

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index d9a73c7683ea3493543eac76f93bbe20023b9bc4..47b6156f5b2c96ae6016f21b39a07ce4ffa04872 100644 (file)
--- 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);