Commit c557d392 authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
Browse files

serial: Test for no tx data on tx restart 



Commit 717f3bba,
'serial_core: Fix conditional start_tx on ring buffer not empty'
exposes an incorrect assumption in several drivers' start_tx methods;
the tx ring buffer can, in fact, be empty when restarting tx while
performing flow control.

Affected drivers:
sunsab.c
ip22zilog.c
pmac_zilog.c
sunzilog.c
m32r_sio.c
imx.c

Other in-tree serial drivers either are not affected or already
test for empty tx ring buffer before transmitting.

Test for empty tx ring buffer in start_tx() method, after transmitting
x_char (if applicable).

Reported-by: default avatarAaro Koskinen <aaro.koskinen@iki.fi>
Cc: Seth Bollinger <sethb@digi.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Cc: stable <stable@vger.kernel.org> # 3.15
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent cd3de83f

drivers/tty/serial/imx.c

+3 −0
Original line number Diff line number Diff line
@@ -567,6 +567,9 @@ static void imx_start_tx(struct uart_port *port) 
	struct imx_port *sport = (struct imx_port *)port;

	unsigned long temp;



	if (uart_circ_empty(&port.state->xmit))

		return;



	if (USE_IRDA(sport)) {

		/* half duplex in IrDA mode; have to disable receive mode */

		temp = readl(sport->port.membase + UCR4);

drivers/tty/serial/ip22zilog.c

+2 −0
Original line number Diff line number Diff line
@@ -603,6 +603,8 @@ static void ip22zilog_start_tx(struct uart_port *port) 
	} else {

		struct circ_buf *xmit = &port->state->xmit;



		if (uart_circ_empty(xmit))

			return;

		writeb(xmit->buf[xmit->tail], &channel->data);

		ZSDELAY();

		ZS_WSYNC(channel);

drivers/tty/serial/m32r_sio.c

+5 −3
Original line number Diff line number Diff line
@@ -266,10 +266,12 @@ static void m32r_sio_start_tx(struct uart_port *port) 
	if (!(up->ier & UART_IER_THRI)) {

		up->ier |= UART_IER_THRI;

		serial_out(up, UART_IER, up->ier);

		if (!uart_circ_empty(xmit)) {

			serial_out(up, UART_TX, xmit->buf[xmit->tail]);

			xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);

			up->port.icount.tx++;

		}

	}

	while((serial_in(up, UART_LSR) & UART_EMPTY) != UART_EMPTY);

#else

	struct uart_sio_port *up = (struct uart_sio_port *)port;

drivers/tty/serial/pmac_zilog.c

+3 −0
Original line number Diff line number Diff line
@@ -653,6 +653,8 @@ static void pmz_start_tx(struct uart_port *port) 
	} else {

		struct circ_buf *xmit = &port->state->xmit;



		if (uart_circ_empty(xmit))

			goto out;

		write_zsdata(uap, xmit->buf[xmit->tail]);

		zssync(uap);

		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
@@ -661,6 +663,7 @@ static void pmz_start_tx(struct uart_port *port) 
		if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)

			uart_write_wakeup(&uap->port);

	}

 out:

	pmz_debug("pmz: start_tx() done.\n");

}

drivers/tty/serial/sunsab.c

+3 −0
Original line number Diff line number Diff line
@@ -427,6 +427,9 @@ static void sunsab_start_tx(struct uart_port *port) 
	struct circ_buf *xmit = &up->port.state->xmit;

	int i;



	if (uart_circ_empty(xmit))

		return;



	up->interrupt_mask1 &= ~(SAB82532_IMR1_ALLS|SAB82532_IMR1_XPR);

	writeb(up->interrupt_mask1, &up->regs->w.imr1);

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