tty: serial: fsl_lpuart: avoid checking for transfer complete when UARTCTRL_SBK is...

According to LPUART RM, Transmission Complete Flag becomes 0 if queuing
a break character by writing 1 to CTRL[SBK], so here need to avoid
checking for transmission complete when UARTCTRL_SBK is asserted,
otherwise the lpuart32_tx_empty may never get TIOCSER_TEMT.

Commit 2411fd94ceaa("tty: serial: fsl_lpuart: skip waiting for
transmission complete when UARTCTRL_SBK is asserted") only fix it in
lpuart32_set_termios(), here also fix it in lpuart32_tx_empty().

Fixes: 380c966c093e ("tty: serial: fsl_lpuart: add 32-bit register interface support")
Cc: stable <stable@kernel.org>
Signed-off-by: Sherry Sun <sherry.sun@nxp.com>
Link: https://lore.kernel.org/r/20230323054415.20363-1-sherry.sun@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index 56e6ba3..edc6e35 100644 (file)
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -858,11 +858,17 @@ static unsigned int lpuart32_tx_empty(struct uart_port *port)
                        struct lpuart_port, port);
        unsigned long stat = lpuart32_read(port, UARTSTAT);
        unsigned long sfifo = lpuart32_read(port, UARTFIFO);
+       unsigned long ctrl = lpuart32_read(port, UARTCTRL);
 
        if (sport->dma_tx_in_progress)
                return 0;
 
-       if (stat & UARTSTAT_TC && sfifo & UARTFIFO_TXEMPT)
+       /*
+        * LPUART Transmission Complete Flag may never be set while queuing a break
+        * character, so avoid checking for transmission complete when UARTCTRL_SBK
+        * is asserted.
+        */
+       if ((stat & UARTSTAT_TC && sfifo & UARTFIFO_TXEMPT) || ctrl & UARTCTRL_SBK)
                return TIOCSER_TEMT;
 
        return 0;