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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>
This commit is contained in:
Hoan Nguyen An 2019-03-18 18:26:32 +09:00 committed by Greg Kroah-Hartman
parent 72ff51d8dd
commit 93bcefd4c6
1 changed files with 1 additions and 11 deletions
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12
drivers/tty/serial/sh-sci.c
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@ -838,19 +838,9 @@ static void sci_transmit_chars(struct uart_port *port)
if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS) if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
uart_write_wakeup(port); uart_write_wakeup(port);
if (uart_circ_empty(xmit)) { if (uart_circ_empty(xmit))
sci_stop_tx(port); 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 */ /* On SH3, SCIF may read end-of-break as a space->mark char */