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Commit 325608ab authored by Sherry Sun's avatar Sherry Sun Committed by Greg Kroah-Hartman
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tty: serial: fsl_lpuart: skip waiting for transmission complete when UARTCTRL_SBK is asserted 



commit 2411fd94ceaa6e11326e95d6ebf876cbfed28d23 upstream.

According to LPUART RM, Transmission Complete Flag becomes 0 if queuing
a break character by writing 1 to CTRL[SBK], so here need to skip
waiting for transmission complete when UARTCTRL_SBK is asserted,
otherwise the kernel may stuck here.
And actually set_termios() adds transmission completion waiting to avoid
data loss or data breakage when changing the baud rate, but we don't
need to worry about this when queuing break characters.

Signed-off-by: default avatarSherry Sun <sherry.sun@nxp.com>
Cc: stable <stable@kernel.org>
Link: https://lore.kernel.org/r/20230223093941.31790-1-sherry.sun@nxp.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent c16cbd82

drivers/tty/serial/fsl_lpuart.c

+9 −3
Original line number Diff line number Diff line
@@ -2002,9 +2002,15 @@ lpuart32_set_termios(struct uart_port *port, struct ktermios *termios, 
	/* update the per-port timeout */

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



	/* wait transmit engin complete */

	/*

	 * 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(&sport->port, 0, UARTMODIR);

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

	}



	/* disable transmit and receive */

	lpuart32_write(&sport->port, old_ctrl & ~(UARTCTRL_TE | UARTCTRL_RE),