[PATCH 5.4 23/68] serial: mvebu-uart: fix drivers tx_empty callback

[Greg Kroah-Hartman]

From: Pali Rohár <pali@xxxxxxxxxx>

commit 74e1eb3b4a1ef2e564b4bdeb6e92afe844e900de upstream.

Driver's tx_empty callback should signal when the transmit shift register
is empty. So when the last character has been sent.

STAT_TX_FIFO_EMP bit signals only that HW transmit FIFO is empty, which
happens when the last byte is loaded into transmit shift register.

STAT_TX_EMP bit signals when the both HW transmit FIFO and transmit shift
register are empty.

So replace STAT_TX_FIFO_EMP check by STAT_TX_EMP in mvebu_uart_tx_empty()
callback function.

Fixes: 30530791a7a0 ("serial: mvebu-uart: initial support for Armada-3700 serial port")
Cc: stable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Pali Rohár <pali@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20210911132017.25505-1-pali@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/tty/serial/mvebu-uart.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/tty/serial/mvebu-uart.c
+++ b/drivers/tty/serial/mvebu-uart.c
@@ -164,7 +164,7 @@ static unsigned int mvebu_uart_tx_empty(
 	st = readl(port->membase + UART_STAT);
 	spin_unlock_irqrestore(&port->lock, flags);
 
-	return (st & STAT_TX_FIFO_EMP) ? TIOCSER_TEMT : 0;
+	return (st & STAT_TX_EMP) ? TIOCSER_TEMT : 0;
 }
 
 static unsigned int mvebu_uart_get_mctrl(struct uart_port *port)