1 files changed, 50 insertions, 5 deletions

diff --git a/drivers/usb/host/xhci-dbgtty.c b/drivers/usb/host/xhci-dbgtty.c
index b8e78867e25a..d719c16ea30b 100644
--- a/drivers/usb/host/xhci-dbgtty.c
+++ b/drivers/usb/host/xhci-dbgtty.c
@@ -24,6 +24,29 @@ static inline struct dbc_port *dbc_to_port(struct xhci_dbc *dbc)
 	return dbc->priv;
 }
 
+static unsigned int
+dbc_kfifo_to_req(struct dbc_port *port, char *packet)
+{
+	unsigned int	len;
+
+	len = kfifo_len(&port->port.xmit_fifo);
+
+	if (len == 0)
+		return 0;
+
+	len = min(len, DBC_MAX_PACKET);
+
+	if (port->tx_boundary)
+		len = min(port->tx_boundary, len);
+
+	len = kfifo_out(&port->port.xmit_fifo, packet, len);
+
+	if (port->tx_boundary)
+		port->tx_boundary -= len;
+
+	return len;
+}
+
 static int dbc_start_tx(struct dbc_port *port)
 	__releases(&port->port_lock)
 	__acquires(&port->port_lock)
@@ -36,7 +59,7 @@ static int dbc_start_tx(struct dbc_port *port)
 
 	while (!list_empty(pool)) {
 		req = list_entry(pool->next, struct dbc_request, list_pool);
-		len = kfifo_out(&port->port.xmit_fifo, req->buf, DBC_MAX_PACKET);
+		len = dbc_kfifo_to_req(port, req->buf);
 		if (len == 0)
 			break;
 		do_tty_wake = true;
@@ -200,14 +223,32 @@ static ssize_t dbc_tty_write(struct tty_struct *tty, const u8 *buf,
 {
 	struct dbc_port		*port = tty->driver_data;
 	unsigned long		flags;
+	unsigned int		written = 0;
 
 	spin_lock_irqsave(&port->port_lock, flags);
-	if (count)
-		count = kfifo_in(&port->port.xmit_fifo, buf, count);
-	dbc_start_tx(port);
+
+	/*
+	 * Treat tty write as one usb transfer. Make sure the writes are turned
+	 * into TRB request having the same size boundaries as the tty writes.
+	 * Don't add data to kfifo before previous write is turned into TRBs
+	 */
+	if (port->tx_boundary) {
+		spin_unlock_irqrestore(&port->port_lock, flags);
+		return 0;
+	}
+
+	if (count) {
+		written = kfifo_in(&port->port.xmit_fifo, buf, count);
+
+		if (written == count)
+			port->tx_boundary = kfifo_len(&port->port.xmit_fifo);
+
+		dbc_start_tx(port);
+	}
+
 	spin_unlock_irqrestore(&port->port_lock, flags);
 
-	return count;
+	return written;
 }
 
 static int dbc_tty_put_char(struct tty_struct *tty, u8 ch)
@@ -241,6 +282,10 @@ static unsigned int dbc_tty_write_room(struct tty_struct *tty)
 
 	spin_lock_irqsave(&port->port_lock, flags);
 	room = kfifo_avail(&port->port.xmit_fifo);
+
+	if (port->tx_boundary)
+		room = 0;
+
 	spin_unlock_irqrestore(&port->port_lock, flags);
 
 	return room;