linux-kernel - [PATCH] serial: mvebu-uart: fix driver's tx

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Date:   Sat, 11 Sep 2021 15:20:17 +0200
From:   Pali Rohár <pali@...nel.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>
Cc:     Russell King <rmk+kernel@...linux.org.uk>,
        Andrew Lunn <andrew@...n.ch>,
        Marek Behún <kabel@...nel.org>,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] serial: mvebu-uart: fix driver's tx_empty callback

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.

Signed-off-by: Pali Rohár <pali@...nel.org>
Fixes: 30530791a7a0 ("serial: mvebu-uart: initial support for Armada-3700 serial port")
---
 drivers/tty/serial/mvebu-uart.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/serial/mvebu-uart.c b/drivers/tty/serial/mvebu-uart.c
index 590f58176dc3..56ba7180f66d 100644
--- a/drivers/tty/serial/mvebu-uart.c
+++ b/drivers/tty/serial/mvebu-uart.c
@@ -191,7 +191,7 @@ static unsigned int mvebu_uart_tx_empty(struct uart_port *port)
 	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)
-- 
2.20.1