Commit 93bcefd4 authored Mar 18, 2019 by Hoan Nguyen An Committed by Greg Kroah-Hartman Mar 19, 2019

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>

parent 72ff51d8

drivers/tty/serial/sh-sci.c

+1 −11

Original line number	Diff line number	Diff line
		@@ -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 */

Admin message