serial: max310x: Fix tx_empty() callback

Function max310x_tx_empty() accesses the IRQSTS register, which is
cleared by IC when reading, so if there is an interrupt status, we
will lose it. This patch implement the transmitter check only by
the current FIFO level.

Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/max310x.c b/drivers/tty/serial/max310x.c
index 3db48fcd6068d853f2c3376c885289222a063d10..4f479841769a1043ea57ecf5f51275ad04093cce 100644 (file)
--- a/drivers/tty/serial/max310x.c
+++ b/drivers/tty/serial/max310x.c
@@ -833,12 +833,9 @@ static void max310x_wq_proc(struct work_struct *ws)
 
 static unsigned int max310x_tx_empty(struct uart_port *port)
 {
-       unsigned int lvl, sts;
+       u8 lvl = max310x_port_read(port, MAX310X_TXFIFOLVL_REG);
 
-       lvl = max310x_port_read(port, MAX310X_TXFIFOLVL_REG);
-       sts = max310x_port_read(port, MAX310X_IRQSTS_REG);
-
-       return ((sts & MAX310X_IRQ_TXEMPTY_BIT) && !lvl) ? TIOCSER_TEMT : 0;
+       return lvl ? 0 : TIOCSER_TEMT;
 }
 
 static unsigned int max310x_get_mctrl(struct uart_port *port)