Commit e98ab45e authored by Sherry Sun's avatar Sherry Sun Committed by Greg Kroah-Hartman
Browse files

tty: serial: lpuart: only disable CTS instead of overwriting the whole UARTMODIR register 



No need to overwrite the whole UARTMODIR register before waiting the
transmit engine complete, actually our target here is only to disable
CTS flow control to avoid the dirty data in TX FIFO may block the
transmit engine complete.
Also delete the following duplicate CTS disable configuration.

Fixes: d5a2e083 ("tty: serial: lpuart: disable flow control while waiting for the transmit engine to complete")
Cc: stable <stable@kernel.org>
Signed-off-by: default avatarSherry Sun <sherry.sun@nxp.com>
Link: https://lore.kernel.org/r/20250307065446.1122482-1-sherry.sun@nxp.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 3c3cede0

drivers/tty/serial/fsl_lpuart.c

+7 −5
Original line number Diff line number Diff line
@@ -2349,15 +2349,19 @@ lpuart32_set_termios(struct uart_port *port, struct ktermios *termios, 
	/* update the per-port timeout */

	uart_update_timeout(port, termios->c_cflag, baud);



	/*

	 * disable CTS to ensure the transmit engine is not blocked by the flow

	 * control when there is dirty data in TX FIFO

	 */

	lpuart32_write(port, modem & ~UARTMODIR_TXCTSE, UARTMODIR);



	/*

	 * LPUART Transmission Complete Flag may never be set while queuing a break

	 * character, so skip waiting for transmission complete when UARTCTRL_SBK is

	 * asserted.

	 */

	if (!(old_ctrl & UARTCTRL_SBK)) {

		lpuart32_write(port, 0, UARTMODIR);

	if (!(old_ctrl & UARTCTRL_SBK))

		lpuart32_wait_bit_set(port, UARTSTAT, UARTSTAT_TC);

	}



	/* disable transmit and receive */

	lpuart32_write(port, old_ctrl & ~(UARTCTRL_TE | UARTCTRL_RE),
@@ -2365,8 +2369,6 @@ lpuart32_set_termios(struct uart_port *port, struct ktermios *termios, 


	lpuart32_write(port, bd, UARTBAUD);

	lpuart32_serial_setbrg(sport, baud);

	/* disable CTS before enabling UARTCTRL_TE to avoid pending idle preamble */

	lpuart32_write(port, modem & ~UARTMODIR_TXCTSE, UARTMODIR);

	/* restore control register */

	lpuart32_write(port, ctrl, UARTCTRL);

	/* re-enable the CTS if needed */