[PATCH 5.15 65/93] tty: serial: fsl_lpuart: avoid checking for transfer complete when UARTCTRL_SBK is asserted in lpuart32_tx_empty

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From: Sherry Sun <sherry.sun@xxxxxxx>

commit 9425914f3de6febbd6250395f56c8279676d9c3c 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 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@xxxxxxxxxx>
Signed-off-by: Sherry Sun <sherry.sun@xxxxxxx>
Link: https://lore.kernel.org/r/20230323054415.20363-1-sherry.sun@xxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/tty/serial/fsl_lpuart.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -829,11 +829,17 @@ static unsigned int lpuart32_tx_empty(st
 			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;





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