1 files changed, 60 insertions, 34 deletions

diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index d9d87111f9a9..21c053c31b9e 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -89,6 +89,7 @@ struct ftdi_private {
         int force_rtscts;       /* if non-zero, force RTS-CTS to always
                                    be enabled */
 
+        unsigned int latency;           /* latency setting in use */
         spinlock_t tx_lock;     /* spinlock for transmit state */
         unsigned long tx_bytes;
         unsigned long tx_outstanding_bytes;
@@ -1038,7 +1039,54 @@ static int change_speed(struct tty_struct *tty, struct usb_serial_port *port)
         return rv;
 }
 
+static int write_latency_timer(struct usb_serial_port *port)
+{
+        struct ftdi_private *priv = usb_get_serial_port_data(port);
+        struct usb_device *udev = port->serial->dev;
+        char buf[1];
+        int rv = 0;
+        int l = priv->latency;
+
+        if (priv->flags & ASYNC_LOW_LATENCY)
+                l = 1;
+
+        dbg("%s: setting latency timer = %i", __func__, l);
+
+        rv = usb_control_msg(udev,
+                             usb_sndctrlpipe(udev, 0),
+                             FTDI_SIO_SET_LATENCY_TIMER_REQUEST,
+                             FTDI_SIO_SET_LATENCY_TIMER_REQUEST_TYPE,
+                             l, priv->interface,
+                             buf, 0, WDR_TIMEOUT);
 
+        if (rv < 0)
+                dev_err(&port->dev, "Unable to write latency timer: %i\n", rv);
+        return rv;
+}
+
+static int read_latency_timer(struct usb_serial_port *port)
+{
+        struct ftdi_private *priv = usb_get_serial_port_data(port);
+        struct usb_device *udev = port->serial->dev;
+        unsigned short latency = 0;
+        int rv = 0;
+
+
+        dbg("%s", __func__);
+
+        rv = usb_control_msg(udev,
+                             usb_rcvctrlpipe(udev, 0),
+                             FTDI_SIO_GET_LATENCY_TIMER_REQUEST,
+                             FTDI_SIO_GET_LATENCY_TIMER_REQUEST_TYPE,
+                             0, priv->interface,
+                             (char *) &latency, 1, WDR_TIMEOUT);
+
+        if (rv < 0) {
+                dev_err(&port->dev, "Unable to read latency timer: %i\n", rv);
+                return -EIO;
+        }
+        return latency;
+}
 
 static int get_serial_info(struct usb_serial_port *port,
                                 struct serial_struct __user *retinfo)
@@ -1098,6 +1146,7 @@ static int set_serial_info(struct tty_struct *tty,
         priv->custom_divisor = new_serial.custom_divisor;
 
         tty->low_latency = (priv->flags & ASYNC_LOW_LATENCY) ? 1 : 0;
+        write_latency_timer(port);
 
 check_and_exit:
         if ((old_priv.flags & ASYNC_SPD_MASK) !=
@@ -1193,27 +1242,13 @@ static ssize_t show_latency_timer(struct device *dev,
 {
         struct usb_serial_port *port = to_usb_serial_port(dev);
         struct ftdi_private *priv = usb_get_serial_port_data(port);
-        struct usb_device *udev = port->serial->dev;
-        unsigned short latency = 0;
-        int rv = 0;
-
-
-        dbg("%s", __func__);
-
-        rv = usb_control_msg(udev,
-                             usb_rcvctrlpipe(udev, 0),
-                             FTDI_SIO_GET_LATENCY_TIMER_REQUEST,
-                             FTDI_SIO_GET_LATENCY_TIMER_REQUEST_TYPE,
-                             0, priv->interface,
-                             (char *) &latency, 1, WDR_TIMEOUT);
-
-        if (rv < 0) {
-                dev_err(dev, "Unable to read latency timer: %i\n", rv);
-                return -EIO;
-        }
-        return sprintf(buf, "%i\n", latency);
+        if (priv->flags & ASYNC_LOW_LATENCY)
+                return sprintf(buf, "1\n");
+        else
+                return sprintf(buf, "%i\n", priv->latency);
 }
 
+
 /* Write a new value of the latency timer, in units of milliseconds. */
 static ssize_t store_latency_timer(struct device *dev,
                         struct device_attribute *attr, const char *valbuf,
@@ -1221,25 +1256,13 @@ static ssize_t store_latency_timer(struct device *dev,
 {
         struct usb_serial_port *port = to_usb_serial_port(dev);
         struct ftdi_private *priv = usb_get_serial_port_data(port);
-        struct usb_device *udev = port->serial->dev;
-        char buf[1];
         int v = simple_strtoul(valbuf, NULL, 10);
         int rv = 0;
 
-        dbg("%s: setting latency timer = %i", __func__, v);
-
-        rv = usb_control_msg(udev,
-                             usb_sndctrlpipe(udev, 0),
-                             FTDI_SIO_SET_LATENCY_TIMER_REQUEST,
-                             FTDI_SIO_SET_LATENCY_TIMER_REQUEST_TYPE,
-                             v, priv->interface,
-                             buf, 0, WDR_TIMEOUT);
-
-        if (rv < 0) {
-                dev_err(dev, "Unable to write latency timer: %i\n", rv);
+        priv->latency = v;
+        rv = write_latency_timer(port);
+        if (rv < 0)
                 return -EIO;
-        }
-
         return count;
 }
 
@@ -1393,6 +1416,7 @@ static int ftdi_sio_port_probe(struct usb_serial_port *port)
         usb_set_serial_port_data(port, priv);
 
         ftdi_determine_type(port);
+        read_latency_timer(port);
         create_sysfs_attrs(port);
         return 0;
 }
@@ -1515,6 +1539,8 @@ static int ftdi_open(struct tty_struct *tty,
         if (tty)
                 tty->low_latency = (priv->flags & ASYNC_LOW_LATENCY) ? 1 : 0;
 
+        write_latency_timer(port);
+
         /* No error checking for this (will get errors later anyway) */
         /* See ftdi_sio.h for description of what is reset */
         usb_control_msg(dev, usb_sndctrlpipe(dev, 0),