TTY/Serial fixes for 3.12-rc3

Here are some serial at tty driver fixes for 3.12-rc3
 
 The serial driver fixes some kref leaks, documentation is moved to the proper
 places, and the tty and n_tty fixes resolve some reported regressions.  There
 is still one outstanding tty regression fix that isn't in here yet, as I want
 to test it out some more, it will be sent for 3.12-rc4 if it checks out.
 
 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Merge tag 'tty-3.12-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

Pull tty/serial fixes from Greg KH:
 "Here are some serial at tty driver fixes for 3.12-rc3

  The serial driver fixes some kref leaks, documentation is moved to the
  proper places, and the tty and n_tty fixes resolve some reported
  regressions.  There is still one outstanding tty regression fix that
  isn't in here yet, as I want to test it out some more, it will be sent
  for 3.12-rc4 if it checks out"

* tag 'tty-3.12-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
  tty: ar933x_uart: move devicetree binding documentation
  tty: Fix SIGTTOU not sent with tcflush()
  n_tty: Fix EOF push index when termios changes
  serial: pch_uart: remove unnecessary tty_port_tty_get
  serial: pch_uart: fix tty-kref leak in dma-rx path
  serial: pch_uart: fix tty-kref leak in rx-error path
  serial: tegra: fix tty-kref leak

drivers/tty/n_tty.c

@@ -1758,8 +1758,7 @@ static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
 		canon_change = (old->c_lflag ^ tty->termios.c_lflag) & ICANON;
 	if (canon_change) {
 		bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
-		ldata->line_start = 0;
-		ldata->canon_head = ldata->read_tail;
+		ldata->line_start = ldata->canon_head = ldata->read_tail;
 		ldata->erasing = 0;
 		ldata->lnext = 0;
 	}

drivers/tty/serial/pch_uart.c

@@ -667,30 +667,21 @@ static int pop_tx_x(struct eg20t_port *priv, unsigned char *buf)
 
 static int dma_push_rx(struct eg20t_port *priv, int size)
 {
-	struct tty_struct *tty;
 	int room;
 	struct uart_port *port = &priv->port;
 	struct tty_port *tport = &port->state->port;
 
-	port = &priv->port;
-	tty = tty_port_tty_get(tport);
-	if (!tty) {
-		dev_dbg(priv->port.dev, "%s:tty is busy now", __func__);
-		return 0;
-	}
-
 	room = tty_buffer_request_room(tport, size);
 
 	if (room < size)
 		dev_warn(port->dev, "Rx overrun: dropping %u bytes\n",
 			 size - room);
 	if (!room)
-		return room;
+		return 0;
 
 	tty_insert_flip_string(tport, sg_virt(&priv->sg_rx), size);
 
 	port->icount.rx += room;
-	tty_kref_put(tty);
 
 	return room;
 }
@@ -1098,6 +1089,8 @@ static void pch_uart_err_ir(struct eg20t_port *priv, unsigned int lsr)
 	if (tty == NULL) {
 		for (i = 0; error_msg[i] != NULL; i++)
 			dev_err(&priv->pdev->dev, error_msg[i]);
+	} else {
+		tty_kref_put(tty);
 	}
 }
 

drivers/tty/serial/serial-tegra.c

@@ -732,7 +732,7 @@ static irqreturn_t tegra_uart_isr(int irq, void *data)
 static void tegra_uart_stop_rx(struct uart_port *u)
 {
 	struct tegra_uart_port *tup = to_tegra_uport(u);
-	struct tty_struct *tty = tty_port_tty_get(&tup->uport.state->port);
+	struct tty_struct *tty;
 	struct tty_port *port = &u->state->port;
 	struct dma_tx_state state;
 	unsigned long ier;
@@ -744,6 +744,8 @@ static void tegra_uart_stop_rx(struct uart_port *u)
 	if (!tup->rx_in_progress)
 		return;
 
+	tty = tty_port_tty_get(&tup->uport.state->port);
+
 	tegra_uart_wait_sym_time(tup, 1); /* wait a character interval */
 
 	ier = tup->ier_shadow;

drivers/tty/tty_ioctl.c

@@ -1201,6 +1201,9 @@ int n_tty_ioctl_helper(struct tty_struct *tty, struct file *file,
 		}
 		return 0;
 	case TCFLSH:
+		retval = tty_check_change(tty);
+		if (retval)
+			return retval;
 		return __tty_perform_flush(tty, arg);
 	default:
 		/* Try the mode commands */