serial: Test for no tx data on tx restart
Commit 717f3bbab3
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'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: Aaro 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: Peter Hurley <peter@hurleysoftware.com>
Cc: stable <stable@vger.kernel.org> # 3.15
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
parent
cd3de83f14
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@ -567,6 +567,9 @@ static void imx_start_tx(struct uart_port *port)
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struct imx_port *sport = (struct imx_port *)port;
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unsigned long temp;
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if (uart_circ_empty(&port.state->xmit))
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return;
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if (USE_IRDA(sport)) {
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/* half duplex in IrDA mode; have to disable receive mode */
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temp = readl(sport->port.membase + UCR4);
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@ -603,6 +603,8 @@ static void ip22zilog_start_tx(struct uart_port *port)
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} else {
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struct circ_buf *xmit = &port->state->xmit;
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if (uart_circ_empty(xmit))
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return;
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writeb(xmit->buf[xmit->tail], &channel->data);
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ZSDELAY();
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ZS_WSYNC(channel);
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@ -266,9 +266,11 @@ static void m32r_sio_start_tx(struct uart_port *port)
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if (!(up->ier & UART_IER_THRI)) {
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up->ier |= UART_IER_THRI;
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serial_out(up, UART_IER, up->ier);
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serial_out(up, UART_TX, xmit->buf[xmit->tail]);
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xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
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up->port.icount.tx++;
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if (!uart_circ_empty(xmit)) {
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serial_out(up, UART_TX, xmit->buf[xmit->tail]);
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xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
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up->port.icount.tx++;
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}
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}
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while((serial_in(up, UART_LSR) & UART_EMPTY) != UART_EMPTY);
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#else
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@ -653,6 +653,8 @@ static void pmz_start_tx(struct uart_port *port)
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} else {
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struct circ_buf *xmit = &port->state->xmit;
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if (uart_circ_empty(xmit))
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goto out;
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write_zsdata(uap, xmit->buf[xmit->tail]);
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zssync(uap);
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xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
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@ -661,6 +663,7 @@ static void pmz_start_tx(struct uart_port *port)
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if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
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uart_write_wakeup(&uap->port);
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}
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out:
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pmz_debug("pmz: start_tx() done.\n");
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}
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@ -427,6 +427,9 @@ static void sunsab_start_tx(struct uart_port *port)
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struct circ_buf *xmit = &up->port.state->xmit;
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int i;
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if (uart_circ_empty(xmit))
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return;
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up->interrupt_mask1 &= ~(SAB82532_IMR1_ALLS|SAB82532_IMR1_XPR);
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writeb(up->interrupt_mask1, &up->regs->w.imr1);
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@ -703,6 +703,8 @@ static void sunzilog_start_tx(struct uart_port *port)
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} else {
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struct circ_buf *xmit = &port->state->xmit;
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if (uart_circ_empty(xmit))
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return;
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writeb(xmit->buf[xmit->tail], &channel->data);
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ZSDELAY();
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ZS_WSYNC(channel);
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