Commit f5cb528d authored by Sherry Sun's avatar Sherry Sun Committed by Greg Kroah-Hartman
Browse files

tty: serial: fsl_lpuart: disable transmitter before changing RS485 related registers 



According to the LPUART reference manual, TXRTSE and TXRTSPOL of MODIR
register only can be changed when the transmitter is disabled.
So disable the transmitter before changing RS485 related registers and
re-enable it after the change is done.

Fixes: 67b01837 ("tty: serial: lpuart: Add RS485 support for 32-bit uart flavour")
Cc: stable <stable@kernel.org>
Signed-off-by: default avatarSherry Sun <sherry.sun@nxp.com>
Reviewed-by: default avatarFrank Li <Frank.Li@nxp.com>
Link: https://lore.kernel.org/r/20250312022503.1342990-1-sherry.sun@nxp.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 5c7e2896

drivers/tty/serial/fsl_lpuart.c

+17 −0
Original line number Diff line number Diff line
@@ -1484,6 +1484,19 @@ static int lpuart32_config_rs485(struct uart_port *port, struct ktermios *termio 


	unsigned long modem = lpuart32_read(&sport->port, UARTMODIR)

				& ~(UARTMODIR_TXRTSPOL | UARTMODIR_TXRTSE);

	u32 ctrl;



	/* TXRTSE and TXRTSPOL only can be changed when transmitter is disabled. */

	ctrl = lpuart32_read(&sport->port, UARTCTRL);

	if (ctrl & UARTCTRL_TE) {

		/* wait for the transmit engine to complete */

		lpuart32_wait_bit_set(&sport->port, UARTSTAT, UARTSTAT_TC);

		lpuart32_write(&sport->port, ctrl & ~UARTCTRL_TE, UARTCTRL);



		while (lpuart32_read(&sport->port, UARTCTRL) & UARTCTRL_TE)

			cpu_relax();

	}



	lpuart32_write(&sport->port, modem, UARTMODIR);



	if (rs485->flags & SER_RS485_ENABLED) {
@@ -1503,6 +1516,10 @@ static int lpuart32_config_rs485(struct uart_port *port, struct ktermios *termio 
	}



	lpuart32_write(&sport->port, modem, UARTMODIR);



	if (ctrl & UARTCTRL_TE)

		lpuart32_write(&sport->port, ctrl, UARTCTRL);



	return 0;

}