TTY/Serial fixes for 3.15-rc3

Here are a few tty/serial fixes for 3.15-rc3 that resolve a number of
 reported issues in the 8250 and samsung serial drivers, as well as a
 character loss fix for the tty core that was caused by the lock removal
 patches a release ago.
 
 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Merge tag 'tty-3.15-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

Pull tty/serial fixes from Greg KH:
 "Here are a few tty/serial fixes for 3.15-rc3 that resolve a number of
  reported issues in the 8250 and samsung serial drivers, as well as a
  character loss fix for the tty core that was caused by the lock
  removal patches a release ago"

* tag 'tty-3.15-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
  serial_core: fix uart PORT_UNKNOWN handling
  serial: samsung: Change barrier() to cpu_relax() in console output
  serial: samsung: don't check config for every character
  serial: samsung: Use the passed in "port", fixing kgdb w/ no console
  serial: 8250: Fix thread unsafe __dma_tx_complete function
  8250_core: Fix unwanted TX chars write
  tty: Fix race condition between __tty_buffer_request_room and flush_to_ldisc

drivers/tty/serial/8250/8250_core.c

@@ -1520,7 +1520,7 @@ int serial8250_handle_irq(struct uart_port *port, unsigned int iir)
 			status = serial8250_rx_chars(up, status);
 	}
 	serial8250_modem_status(up);
-	if (status & UART_LSR_THRE)
+	if (!up->dma && (status & UART_LSR_THRE))
 		serial8250_tx_chars(up);
 
 	spin_unlock_irqrestore(&port->lock, flags);

drivers/tty/serial/8250/8250_dma.c

@@ -20,12 +20,15 @@ static void __dma_tx_complete(void *param)
 	struct uart_8250_port	*p = param;
 	struct uart_8250_dma	*dma = p->dma;
 	struct circ_buf		*xmit = &p->port.state->xmit;
-
-	dma->tx_running = 0;
+	unsigned long	flags;
 
 	dma_sync_single_for_cpu(dma->txchan->device->dev, dma->tx_addr,
 				UART_XMIT_SIZE, DMA_TO_DEVICE);
 
+	spin_lock_irqsave(&p->port.lock, flags);
+
+	dma->tx_running = 0;
+
 	xmit->tail += dma->tx_size;
 	xmit->tail &= UART_XMIT_SIZE - 1;
 	p->port.icount.tx += dma->tx_size;
@@ -35,6 +38,8 @@ static void __dma_tx_complete(void *param)
 
 	if (!uart_circ_empty(xmit) && !uart_tx_stopped(&p->port))
 		serial8250_tx_dma(p);
+
+	spin_unlock_irqrestore(&p->port.lock, flags);
 }
 
 static void __dma_rx_complete(void *param)

drivers/tty/serial/samsung.c

@@ -1446,8 +1446,8 @@ static int s3c24xx_serial_get_poll_char(struct uart_port *port)
 static void s3c24xx_serial_put_poll_char(struct uart_port *port,
 		unsigned char c)
 {
-	unsigned int ufcon = rd_regl(cons_uart, S3C2410_UFCON);
-	unsigned int ucon = rd_regl(cons_uart, S3C2410_UCON);
+	unsigned int ufcon = rd_regl(port, S3C2410_UFCON);
+	unsigned int ucon = rd_regl(port, S3C2410_UCON);
 
 	/* not possible to xmit on unconfigured port */
 	if (!s3c24xx_port_configured(ucon))
@@ -1455,7 +1455,7 @@ static void s3c24xx_serial_put_poll_char(struct uart_port *port,
 
 	while (!s3c24xx_serial_console_txrdy(port, ufcon))
 		cpu_relax();
-	wr_regb(cons_uart, S3C2410_UTXH, c);
+	wr_regb(port, S3C2410_UTXH, c);
 }
 
 #endif /* CONFIG_CONSOLE_POLL */
@@ -1463,22 +1463,23 @@ static void s3c24xx_serial_put_poll_char(struct uart_port *port,
 static void
 s3c24xx_serial_console_putchar(struct uart_port *port, int ch)
 {
-	unsigned int ufcon = rd_regl(cons_uart, S3C2410_UFCON);
-	unsigned int ucon = rd_regl(cons_uart, S3C2410_UCON);
-
-	/* not possible to xmit on unconfigured port */
-	if (!s3c24xx_port_configured(ucon))
-		return;
+	unsigned int ufcon = rd_regl(port, S3C2410_UFCON);
 
 	while (!s3c24xx_serial_console_txrdy(port, ufcon))
-		barrier();
-	wr_regb(cons_uart, S3C2410_UTXH, ch);
+		cpu_relax();
+	wr_regb(port, S3C2410_UTXH, ch);
 }
 
 static void
 s3c24xx_serial_console_write(struct console *co, const char *s,
 			     unsigned int count)
 {
+	unsigned int ucon = rd_regl(cons_uart, S3C2410_UCON);
+
+	/* not possible to xmit on unconfigured port */
+	if (!s3c24xx_port_configured(ucon))
+		return;
+
 	uart_console_write(cons_uart, s, count, s3c24xx_serial_console_putchar);
 }
 

drivers/tty/serial/serial_core.c

@@ -136,6 +136,11 @@ static int uart_port_startup(struct tty_struct *tty, struct uart_state *state,
 	if (uport->type == PORT_UNKNOWN)
 		return 1;
 
+	/*
+	 * Make sure the device is in D0 state.
+	 */
+	uart_change_pm(state, UART_PM_STATE_ON);
+
 	/*
 	 * Initialise and allocate the transmit and temporary
 	 * buffer.
@@ -825,25 +830,29 @@ static int uart_set_info(struct tty_struct *tty, struct tty_port *port,
 		 * If we fail to request resources for the
 		 * new port, try to restore the old settings.
 		 */
-		if (retval && old_type != PORT_UNKNOWN) {
+		if (retval) {
 			uport->iobase = old_iobase;
 			uport->type = old_type;
 			uport->hub6 = old_hub6;
 			uport->iotype = old_iotype;
 			uport->regshift = old_shift;
 			uport->mapbase = old_mapbase;
-			retval = uport->ops->request_port(uport);
-			/*
-			 * If we failed to restore the old settings,
-			 * we fail like this.
-			 */
-			if (retval)
-				uport->type = PORT_UNKNOWN;
 
-			/*
-			 * We failed anyway.
-			 */
-			retval = -EBUSY;
+			if (old_type != PORT_UNKNOWN) {
+				retval = uport->ops->request_port(uport);
+				/*
+				 * If we failed to restore the old settings,
+				 * we fail like this.
+				 */
+				if (retval)
+					uport->type = PORT_UNKNOWN;
+
+				/*
+				 * We failed anyway.
+				 */
+				retval = -EBUSY;
+			}
+
 			/* Added to return the correct error -Ram Gupta */
 			goto exit;
 		}
@@ -1570,12 +1579,6 @@ static int uart_open(struct tty_struct *tty, struct file *filp)
 		goto err_dec_count;
 	}
 
-	/*
-	 * Make sure the device is in D0 state.
-	 */
-	if (port->count == 1)
-		uart_change_pm(state, UART_PM_STATE_ON);
-
 	/*
 	 * Start up the serial port.
 	 */

drivers/tty/tty_buffer.c

@@ -255,11 +255,16 @@ static int __tty_buffer_request_room(struct tty_port *port, size_t size,
 	if (change || left < size) {
 		/* This is the slow path - looking for new buffers to use */
 		if ((n = tty_buffer_alloc(port, size)) != NULL) {
+			unsigned long iflags;
+
 			n->flags = flags;
 			buf->tail = n;
+
+			spin_lock_irqsave(&buf->flush_lock, iflags);
 			b->commit = b->used;
-			smp_mb();
 			b->next = n;
+			spin_unlock_irqrestore(&buf->flush_lock, iflags);
+
 		} else if (change)
 			size = 0;
 		else
@@ -443,6 +448,7 @@ static void flush_to_ldisc(struct work_struct *work)
 	mutex_lock(&buf->lock);
 
 	while (1) {
+		unsigned long flags;
 		struct tty_buffer *head = buf->head;
 		int count;
 
@@ -450,14 +456,19 @@ static void flush_to_ldisc(struct work_struct *work)
 		if (atomic_read(&buf->priority))
 			break;
 
+		spin_lock_irqsave(&buf->flush_lock, flags);
 		count = head->commit - head->read;
 		if (!count) {
-			if (head->next == NULL)
+			if (head->next == NULL) {
+				spin_unlock_irqrestore(&buf->flush_lock, flags);
 				break;
+			}
 			buf->head = head->next;
+			spin_unlock_irqrestore(&buf->flush_lock, flags);
 			tty_buffer_free(port, head);
 			continue;
 		}
+		spin_unlock_irqrestore(&buf->flush_lock, flags);
 
 		count = receive_buf(tty, head, count);
 		if (!count)
@@ -512,6 +523,7 @@ void tty_buffer_init(struct tty_port *port)
 	struct tty_bufhead *buf = &port->buf;
 
 	mutex_init(&buf->lock);
+	spin_lock_init(&buf->flush_lock);
 	tty_buffer_reset(&buf->sentinel, 0);
 	buf->head = &buf->sentinel;
 	buf->tail = &buf->sentinel;

include/linux/tty.h

@@ -61,6 +61,7 @@ struct tty_bufhead {
 	struct tty_buffer *head;	/* Queue head */
 	struct work_struct work;
 	struct mutex	   lock;
+	spinlock_t	   flush_lock;
 	atomic_t	   priority;
 	struct tty_buffer sentinel;
 	struct llist_head free;		/* Free queue head */