serial: sh-sci: Fix setting SCSCR_TIE while transferring data

We disable transmission interrupt (clear SCSCR_TIE) after all data has been transmitted
(if uart_circ_empty(xmit)). While transmitting, if the data is still in the tty buffer,
re-enable the SCSCR_TIE bit, which was done at sci_start_tx().
This is unnecessary processing, wasting CPU operation if the data transmission length is large.
And further, transmit end, FIFO empty bits disabling have also been performed in the step above.

Signed-off-by: Hoan Nguyen An <na-hoan@jinso.co.jp>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 060fcd42b6d560105a114c9923ce1cdcc177b696..2d1c626312cd8892d5eae0fa65e03d3347a09e81 100644 (file)
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -838,19 +838,9 @@ static void sci_transmit_chars(struct uart_port *port)
 
        if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
                uart_write_wakeup(port);
-       if (uart_circ_empty(xmit)) {
+       if (uart_circ_empty(xmit))
                sci_stop_tx(port);
-       } else {
-               ctrl = serial_port_in(port, SCSCR);
-
-               if (port->type != PORT_SCI) {
-                       serial_port_in(port, SCxSR); /* Dummy read */
-                       sci_clear_SCxSR(port, SCxSR_TDxE_CLEAR(port));
-               }
 
-               ctrl |= SCSCR_TIE;
-               serial_port_out(port, SCSCR, ctrl);
-       }
 }
 
 /* On SH3, SCIF may read end-of-break as a space->mark char */