[PATCH 6.7 230/309] serial: mxs-auart: fix tx

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6.7-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jiri Slaby (SUSE) <jirislaby@xxxxxxxxxx>

commit 7be50f2e8f20fc2299069b28dea59a28e3abe20a upstream.

Emil reports:
  After updating Linux on an i.MX28 board, serial communication over
  AUART broke. When I TX from the board and measure on the TX pin, it
  seems like the HW fifo is not emptied before the transmission is
  stopped.

MXS performs weird things with stop_tx(). The driver makes it
conditional on uart_tx_stopped().

So the driver needs special handling. Pass the brand new UART_TX_NOSTOP
to uart_port_tx_flags() and handle the stop on its own.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@xxxxxxxxxx>
Reported-by: Emil Kronborg <emil.kronborg@xxxxxxxxxxxxxx>
Cc: stable <stable@xxxxxxxxxx>
Fixes: 2d141e683e9a ("tty: serial: use uart_port_tx() helper")
Closes: https://lore.kernel.org/all/miwgbnvy3hjpnricubg76ytpn7xoceehwahupy25bubbduu23s@om2lptpa26xw/
Tested-by: Stefan Wahren <wahrenst@xxxxxxx>
Tested-by: Emil Kronborg <emil.kronborg@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240201105557.28043-2-jirislaby@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/tty/serial/mxs-auart.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/tty/serial/mxs-auart.c
+++ b/drivers/tty/serial/mxs-auart.c
@@ -605,13 +605,16 @@ static void mxs_auart_tx_chars(struct mx
 		return;
 	}
 
-	pending = uart_port_tx(&s->port, ch,
+	pending = uart_port_tx_flags(&s->port, ch, UART_TX_NOSTOP,
 		!(mxs_read(s, REG_STAT) & AUART_STAT_TXFF),
 		mxs_write(ch, s, REG_DATA));
 	if (pending)
 		mxs_set(AUART_INTR_TXIEN, s, REG_INTR);
 	else
 		mxs_clr(AUART_INTR_TXIEN, s, REG_INTR);
+
+	if (uart_tx_stopped(&s->port))
+               mxs_auart_stop_tx(&s->port);
 }
 
 static void mxs_auart_rx_char(struct mxs_auart_port *s)






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