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tty: serial: fsl_lpuart: skip waiting for transmission complete when UARTCTRL_SBK is asserted

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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: Sherry 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Sherry Sun 2023-02-23 17:39:41 +08:00 committed by Greg Kroah-Hartman
parent c16cbd8233
commit 325608ab60
1 changed files with 9 additions and 3 deletions
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12
drivers/tty/serial/fsl_lpuart.c
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@ -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 */
lpuart32_write(&sport->port, 0, UARTMODIR);
lpuart32_wait_bit_set(&sport->port, UARTSTAT, UARTSTAT_TC);
/*
* 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),